You may see “The program can’t start because dao350.dll is missing,” “The code execution cannot proceed because dao350.dll was not found,” or “Error loading DLL” when an old application starts. dao350.dll is the Microsoft DAO 3.51 Object Library, a 32-bit Microsoft Jet database component that normally belongs to an older application installation, not to modern Windows.
The 60-second answer
Do not download dao350.dll from a random DLL website or copy it into System32.
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The safest repair is:
- Identify the old program that is failing.
- Repair or reinstall that program using its original installer or official vendor media.
- If the correct DLL already exists, register it with the 32-bit
regsvr32.exe. - If registration fails, repair the complete DAO, Jet, Office, Visual Basic, or application installation instead of adding unrelated DLLs.
On 64-bit Windows, the affected application is usually 32-bit and must use the 32-bit DAO component and the 32-bit registration tool.
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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →What is dao350.dll?
dao350.dll is the Microsoft DAO 3.51 Object Library, associated with Microsoft Jet Database 3.5. DAO, or Data Access Objects, provided older Windows programs with access to Jet databases.
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Microsoft documentation associates Jet 3.5 with products including:
- Access 97 and Office 97
- Visual Basic 5.0
- Visual Basic 6.0 projects and installations
- Excel 97
- Older reporting, accounting, engineering, database, and middleware applications
Microsoft identifies the usual shared location as:
C:Program FilesCommon FilesMicrosoft SharedDAO
On 64-bit Windows, a 32-bit installation may instead use:
C:Program Files (x86)Common FilesMicrosoft SharedDAO
The file is not a normal Windows 10 or Windows 11 system DLL. It is a legacy application component. Microsoft’s Visual Basic support information also distinguishes the obsolete VB6 development environment from the separately supported VB6 runtime components. Those are not the same thing.
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The relevant DAO component is 32-bit. A 64-bit application cannot load it directly, and installing a 64-bit file with the same name would not solve that architecture mismatch.
What the error message usually means
The wording gives you a useful starting point, but it does not always identify the exact cause.
| Message | What it commonly indicates |
|---|---|
Can't find file 'DAO350.DLL' |
The application cannot locate the DAO file in its expected path |
The program can't start because DAO350.dll is missing |
The loader could not start the application with its required dependency |
Error loading DLL |
The file may be present but unregistered, damaged, incompatible, or missing a dependency |
dao350.dll was unable to register itself in the system |
Registration failed, often because of the wrong tool, permissions, architecture, or missing companion files |
The specified module could not be found |
The named file may exist, but another dependency required by it may be missing |
not designed to run on Windows or it contains an error |
The file may be damaged, incompatible, or the wrong build for the application |
A file can therefore be present and still produce a “missing” message. Windows may be reporting a failed load rather than literal file absence.
Fix 1: Repair or reinstall the affected application
This is the most likely solution because dao350.dll is normally installed as part of a legacy program or shared Microsoft component.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesFind the program that needs DAO
Look at the error window, desktop shortcut, Start menu entry, or recent application activity. Typical examples include an old Access database, Visual Basic application, Office installation, accounting tool, reporting utility, engineering program, or game that bundled legacy database components.
If the error appears immediately after uninstalling another application, that uninstall may have removed a shared DAO file needed by the remaining program.
Repair a modern Windows program entry
For an application that supports Windows repair:
- Press Windows + I to open Settings.
- Select Apps.
- Select Installed apps on Windows 11, or Apps & features on Windows 10.
- Find the affected application.
- Select the three-dot menu on Windows 11, or select the application on Windows 10.
- Choose Advanced options if available.
- Select Repair.
- Start the application again.
If Repair does not help, return to the same screen and choose Reset only if the application’s documentation says its data will be preserved. Reset can remove application settings.
For traditional desktop programs:
- Press Windows + R.
- Type
appwiz.cpl. - Press Enter.
- Select the affected program.
- Choose Change, Repair, or Modify if offered.
- Follow the installer prompts.
- Restart Windows and test the application.
If there is no Repair option, uninstall and reinstall the program from its original media or the software vendor’s official installer. For an old Office, Access, or Visual Basic installation, use the original installation source that supplied the component.
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How to tell whether this worked
The repair succeeded if:
- The application starts without the DAO error.
- Its database or project opens normally.
- The error does not return after restarting Windows.
- The program can perform the database operation that previously failed.
If the same message returns, continue with the file and registration checks below.
Fix 2: Check whether the supplied DLL exists
Only inspect files supplied by the affected application or trusted original installation media.
- Press Windows + E.
- Browse to:
text
C:Program FilesCommon FilesMicrosoft SharedDAO
- On 64-bit Windows, also check:
text
C:Program Files (x86)Common FilesMicrosoft SharedDAO
- Look for
dao350.dll. - Right-click the file and choose Properties.
- Open the Details tab.
- Check the description and version information.
Historical installations contain different DAO 3.5 and 3.51 builds. A known VB6-era version string is 3.51.1608.0, but the newest-looking file is not automatically correct for every application. Office 97, Visual Basic 5, Visual Basic 6, and third-party programs may expect different builds.
If the file is absent, do not obtain it from a generic DLL download site. Repair or reinstall the application that supplied it.
If the file exists, registration may be the problem.
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Fix 3: Register the existing 32-bit DAO file
Unlike many ordinary runtime DLLs, DAO350 exposes COM registration entry points. Microsoft’s legacy documentation specifically directs users to register it.
Close the affected application before starting.
On 32-bit Windows
Open an elevated Command Prompt:
- Open the Start menu.
- Type
cmd. - Right-click Command Prompt.
- Select Run as administrator.
- Run the command below, adjusting the path if your file is elsewhere:
%windir%System32regsvr32.exe "C:Program FilesCommon FilesMicrosoft SharedDAOdao350.dll"
Press Enter. A successful registration normally produces a message saying that the operation succeeded.
On 64-bit Windows
Use the 32-bit registration program in SysWOW64:
%windir%SysWOW64regsvr32.exe "C:Program Files (x86)Common FilesMicrosoft SharedDAOdao350.dll"
The names are confusing. On 64-bit Windows:
System32regsvr32.exeis the 64-bit registration tool.SysWOW64regsvr32.exeis the 32-bit registration tool.
Because DAO350 is a 32-bit component, the SysWOW64 command is normally the correct choice for a 32-bit legacy application.
If the command says the module could not be found
Confirm the path first:
dir "C:Program Files (x86)Common FilesMicrosoft SharedDAOdao350.dll"
If Windows reports that the file does not exist, return to application repair or reinstall.
If the file does exist but registration reports a missing module, a companion Jet file or another dependency may be missing. Do not repeatedly copy unrelated DLLs into Windows folders. Repair the complete application or its original DAO/Jet installation.
If registration reports an architecture error
You probably used the wrong regsvr32.exe.
On 64-bit Windows, retry with:
%windir%SysWOW64regsvr32.exe "full-path-to-dao350.dll"
Use the actual path shown in File Explorer. Registration must be performed from an elevated Command Prompt.
Fix 4: Check for an incompatible DAO version
Several older Microsoft products installed different DAO350 builds. A file that works for one application may not be the version expected by another.
This can happen after:
- Installing Office 97, VB5, or VB6 over an existing program
- Repairing or uninstalling an older Microsoft product
- Restoring files from another computer
- Replacing the DLL manually
- Using a cleanup utility
- Installing a third-party application that bundles its own DAO files
The reliable fix is to reinstall the application that currently fails and let its installer restore the expected files and registry entries. Do not replace the file with a newer or larger copy simply because its metadata looks more recent.
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If two legacy applications require incompatible DAO builds, keep them isolated where possible. Use the application’s private installation folder when its vendor supports that arrangement, or ask the vendor for a compatible runtime package.
Fix 5: Check antivirus Protection History
Security software may quarantine a legacy DLL, particularly after a detection, update, or cleanup operation.
In Windows Security:
- Open the Start menu.
- Type Windows Security.
- Open it.
- Select Virus & threat protection.
- Select Protection history.
- Review recent actions.
- Select the event related to the affected application.
- Do not restore the file until you have confirmed that it came from trusted original installation media or the legitimate application installer.
If the file was downloaded from an untrusted website, do not restore it. Remove it and reinstall the application from an official source instead.
Microsoft warns that restoring a quarantined threat can cause it to be detected again. If a trusted installer repeatedly triggers detection, update Windows Security and confirm the installer’s origin before deciding how to proceed.
Fix 6: Repair broader Windows component corruption
This is not the first fix for dao350.dll, because DAO350 is not normally a protected Windows system file. Use these commands when Windows has other corruption symptoms, such as broken system tools, failed updates, or multiple unrelated application errors.
Run DISM
- Open the Start menu.
- Type
cmd. - Right-click Command Prompt.
- Select Run as administrator.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for the operation to finish.
- Restart Windows.
Run System File Checker
Open an elevated Command Prompt again and run:
sfc /scannow
Wait until verification reaches 100 percent, then restart Windows.
DISM and SFC may repair Windows component corruption, but they are not guaranteed to restore a missing DAO installation. If the application still reports dao350.dll, repair or reinstall the application that owns the file.
If you want help identifying which Windows components are damaged rather than repeatedly guessing through DISM and SFC, Outbyte PC Repair can scan for reported issues; its free scan shows what it finds, while repair is handled by the full version. Reinstalling the affected legacy program remains the definitive fix when that program supplied DAO350.
Fix 7: Do not chase unrelated runtimes or drivers
Do not install MDAC just because the error mentions a database
MDAC 2.6 and later do not contain the older Jet components or Jet DAO. Installing MDAC 2.8 is therefore not a guaranteed way to restore DAO350.
Do not treat Access Database Engine as a drop-in replacement
Microsoft’s current Access Database Engine packages provide newer ACE and OLE DB connectivity. They are not guaranteed replacements for DAO 3.51 and may not satisfy an application that specifically expects dao350.dll.
Install a current database engine only when the application vendor explicitly requires that package.
Do not install Visual C++, DirectX, or .NET without evidence
Those runtimes solve different dependency problems. They do not automatically restore Microsoft DAO 3.51.
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Do not reinstall a driver as the normal DAO fix
DAO350 is a database component, not a device driver. Device Manager will not normally repair it.
If the error began alongside a separate device problem, you can check drivers:
- Right-click Start.
- Select Device Manager.
- Expand the relevant category.
- Right-click the affected device.
- Select Update driver.
- Choose Search automatically for drivers.
Only do this for a genuine device problem, not as a response to the DAO error itself.
If manually checking every device and driver is the problem, Outbyte Driver Updater can scan for outdated drivers; its free scan identifies reported issues, while driver installation is handled by the full version. Driver replacement still will not substitute for reinstalling the application that supplied DAO350.
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Windows Features does not provide a standard checkbox that installs DAO 3.51. To inspect available components:
- Press Windows + R.
- Type
optionalfeatures. - Press Enter.
- Review the list without enabling unrelated features.
Do not enable legacy components merely because they sound database-related. Use the application’s documented requirements.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 8: Consider System Restore after a recent change
Use System Restore only when the failure clearly started after a recent uninstall, update, cleanup, or system change and a suitable restore point exists.
- Press Windows + R.
- Type
rstrui.exe. - Press Enter.
- Select Next.
- Choose a restore point from before the problem began.
- Select Scan for affected programs if available.
- Review the changes.
- Select Finish if the restore point is appropriate.
System Restore rolls back system files, registry settings, and installed programs. It does not remove personal files. It may not restore every application file, so reinstall the affected program if the DAO error remains.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteWhat not to do
Avoid these common but unreliable fixes:
- Downloading
dao350.dllfrom a random DLL website - Copying an unknown file into
C:WindowsSystem32 - Copying a 32-bit file into
SysWOW64without understanding the registry view - Registering a DLL from an untrusted source
- Replacing the file with a different DAO build without backing up the application
- Assuming a Microsoft-looking filename proves authenticity
- Installing MDAC, DirectX, Visual C++, or .NET without an application requirement
- Running repeated registration commands after a missing-dependency error
- Disabling antivirus protection to force an unknown DLL into place
A random download can contain malware, use the wrong version, have the wrong architecture, or leave the actual application installation damaged.
Safe sources for the repair
Use, in this order:
- The affected program’s original installer
- Original Office, Access, or Visual Basic installation media
- The software vendor’s official installer or repair package
- Microsoft’s official support and documentation for Windows repair procedures
There is no currently verified Microsoft standalone DAO 3.5 or Jet 3.51 download that should be treated as a general replacement for this file. A modern Microsoft database engine is not automatically compatible with an application built for DAO 3.51.
When the application still will not start
If repair, reinstall, and correct 32-bit registration do not solve the error:
- Confirm whether the application is 32-bit.
- Confirm that
dao350.dllcame from the application’s trusted installer. - Check whether the application has private Jet or DAO files in its own directory.
- Look for a missing-dependency message during registration.
- Test the program with the expected user permissions.
- Contact the application vendor for its legacy runtime package.
- Ask whether the program supports Windows 10 or Windows 11, compatibility mode, or migration to a modern database provider.
Compatibility mode may help an old program run, but it does not create missing DAO files. If the application is abandoned and cannot operate safely, migrating its data to a supported application may be the long-term solution.
FAQ
Is dao350.dll part of Windows 11?
No. dao350.dll is a legacy Microsoft Jet and DAO component normally installed by older applications and development tools.
Is dao350.dll 32-bit or 64-bit?
The relevant DAO 3.5 and 3.51 component is 32-bit. A 32-bit legacy application can run on 64-bit Windows through WOW64, but a 64-bit application cannot load DAO350 directly.
Can I copy dao350.dll into System32?
That is not recommended. It can create version conflicts, incorrect COM registration, and security exposure. Repair the application that supplied the file.
Should I register dao350.dll?
Yes, if the trusted file already exists and the application reports a registration or loading problem. On 64-bit Windows, use the 32-bit tool in SysWOW64.
Why does Windows say the file is missing when I can see it?
The file may not be registered, may be in the wrong location, may have a missing dependency, or may be incompatible with the application’s architecture or expected version.
Will Access Database Engine 2016 fix the problem?
Not necessarily. It is a newer database connectivity product and is not a guaranteed replacement for DAO 3.51.
Will SFC restore dao350.dll?
Not normally. SFC repairs protected Windows system files. DAO350 usually comes from an application installation, so repair or reinstall that application first.
Is the VB6 runtime the same as the VB6 development environment?
No. The development environment and runtime have different support considerations. A program built with VB6 may still require additional DAO components that are not restored merely by installing or repairing the runtime.
What is the final fix for an old program that cannot use DAO350 on Windows 11?
Use the vendor’s supported installer or runtime, run the program in a supported compatibility configuration, or migrate to a newer application and database provider. Do not force an unknown DLL into Windows system folders.
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