Start with this diagnostic checklist
Before replacing anything, identify what is requesting addsccus.dll.
- Which program fails: Visual Basic 6, Microsoft Access Developer tools, Visual SourceSafe, an older office application, or another legacy program.
- When it fails: At Windows sign-in, when launching a shortcut, when opening an old project, or during a source-control operation.
- Where the file should belong: Usually beside the legacy application or inside its installed component folder, not automatically in a Windows system directory.
- Windows architecture: A 32-bit application can run on 64-bit Windows through WOW64.
addsccus.dllis a 32-bit legacy DLL, so a 64-bit version of Windows does not make the file interchangeable with a 64-bit system DLL. - Recent changes: Check whether the problem started after an uninstall, antivirus alert, application update, or migration to a new computer.
addsccus.dll is the Microsoft SourceSafe Add-In Resource DLL, associated with Microsoft Visual SourceSafe and legacy source-control integrations distributed with Visual Basic 6 and Access Developer tools. It is not a normal Windows component. The safest fix is to repair or reinstall the specific application or add-in that originally installed it.
Do not download this file from a random DLL website or copy an unverified replacement into System32 or SysWOW64. That can introduce malware, the wrong architecture, or an incompatible build while leaving the damaged application installation unresolved.
Fix 1: Repair the program that reports the error
This is the most likely solution when the message appears while opening Visual Basic 6, Access Developer tools, SourceSafe, or an older application that uses source control.
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Use Programs and Features
- Close the failing application.
- Press Windows key + R.
- Type
appwiz.cpland press Enter. - Find the relevant entry, such as Visual SourceSafe, Visual Basic tools, Microsoft Access Developer components, Microsoft Office, or the vendor application that uses them.
- Select it and choose Change, Repair, or Modify.
- If the installer displays a feature list, select the SourceSafe, Source Control, Access Developer, or Visual Basic tools component.
- Allow the installer to complete.
- Restart Windows.
- Open the same shortcut or project that produced the error.
A successful repair normally means the original application starts without the missing-file message and its source-control features load normally.
If there is no Repair option, run the original installer from the licensed Microsoft media or your organization’s deployment package. Choose the same product edition and the source-control features that were installed originally. Do not mix a random DLL from another computer with a different product release.
Microsoft’s general desktop-program repair process is described in its program repair guidance.
Reinstall the matching SourceSafe or add-in component
The Access source-code-control integration depends on the Visual SourceSafe client. An add-in can remain installed after the client has been removed, or the client can be damaged while the host application still works.
Use the original installation media or a trusted organizational image to:
- Remove the damaged SourceSafe or source-control component from Control Panel.
- Restart Windows if the installer requests it.
- Run the matching installer as an administrator.
- Install the SourceSafe client and the host application’s source-control integration.
- Restart again.
- Test the original application.
The archived Microsoft documentation for the Access source-code-control component identifies Addsccus.dll as a resource file installed with that component and notes that the Visual SourceSafe client is also required.
Visual SourceSafe is legacy software and is no longer a current supported development platform. If the application is business-critical, preserve the original installer, license information, configuration, and project backups before changing the installation.
Fix 2: Check whether antivirus quarantined the file
Security software may remove or quarantine a legacy DLL, particularly if the file is old or the surrounding application has been modified.
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- Open Start and select Windows Security.
- Select Virus & threat protection.
- Under Current threats, select Protection history.
- Look for an event involving
addsccus.dllor the application that owns it. - Open the event and review its location and detection details.
Restore the file only when all of these conditions are true:
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- The file was located in the expected installation directory.
- The associated SourceSafe, Visual Basic, Access, or vendor software is trusted.
- The installation came from genuine Microsoft media or a known organizational package.
- A current antivirus scan does not identify the file or application as malicious.
- You can establish the file’s provenance, such as through the original installer or a verified deployment image.
Do not restore a copy found in a temporary folder, a random application directory, or an unfamiliar download location. In that situation, leave it quarantined, run a full scan, and reinstall the legitimate application from trusted media.
If the file is repeatedly quarantined after a clean reinstall, contact the security administrator or software vendor rather than creating a broad antivirus exclusion.
Fix 3: Identify the executable or add-in that is loading it
The error may not name the real owner. A stale shortcut, Office add-in, startup entry, or old development project can request the DLL after its parent application has been removed.
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Check the following locations:
Shortcuts
- Right-click the shortcut that triggers the message.
- Select Properties.
- Review the Target and Start in fields.
- Note the executable path.
- Check whether that application is still installed.
If the shortcut points to an obsolete program, delete the shortcut or reinstall the program before removing anything else.
Startup entries
- Press Ctrl + Shift + Esc to open Task Manager.
- Select Startup apps.
- Look for the old IDE, Access add-in, SourceSafe utility, or vendor application.
- Right-click a clearly obsolete entry and choose Disable.
- Restart Windows and test again.
Do not disable unfamiliar security or system entries solely because their names look old.
Installed add-ins
For an Office-based failure, open the affected Office application without opening the problematic document if possible. Review its add-ins and disable an obsolete source-control integration. The exact menu differs between Office generations, so avoid deleting registry values unless the software documentation or an administrator confirms the entry.
If the error appears only for one project, check that project’s source-control configuration. It may reference a provider that no longer exists.
Fix 4: Do not copy the file blindly to System32 or SysWOW64
addsccus.dll is a 32-bit resource DLL, not a standard Windows system file. A 32-bit application on 64-bit Windows normally uses its own application directory and runs under WOW64.
The folders have different purposes:
C:WindowsSystem32is the native system directory on 64-bit Windows.C:WindowsSysWOW64contains 32-bit Windows components on 64-bit Windows.- Neither folder is a general-purpose storage location for application DLLs.
Copying the file to both directories can create confusion and does not install the dependencies, registry settings, add-in configuration, or correct application files. It also may cause an application to load the wrong build.
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A manual replacement is defensible only when it comes from:
- The original Microsoft installation media.
- A trusted organizational deployment image.
- A repaired installation of the same product and version.
- A vendor installer that explicitly includes the file.
Place it in the application’s documented directory only when the installer or product design confirms that location.
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regsvr32 is intended for DLLs that expose a registration entry point such as DllRegisterServer, commonly COM or ActiveX components. addsccus.dll is identified as a SourceSafe add-in resource or localization DLL, not as a self-registering COM server.
These commands are therefore not an evidence-based repair:
regsvr32 addsccus.dll
regsvr32 /i addsccus.dll
If you run them, Windows may report that DllRegisterServer was not found. That does not mean the file needs a different registration switch. Registration cannot recreate a deleted resource, repair the parent application, or install a missing dependency.
Use the application installer instead.
Fix 6: Install only the runtime the application actually needs
Reinstalling Visual C++, DirectX, or .NET is not a first-line fix for addsccus.dll. This file belongs to legacy SourceSafe-related tooling, not to a general Windows runtime package.
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- If it names only
addsccus.dll, repair the owning SourceSafe, VB6, Access Developer, or vendor application. - If it also names a Visual C++ runtime, .NET assembly, or another dependency, follow that application’s official installation instructions for the additional component.
- If the program is a modern game or launcher, use its own file-verification or repair function only when that launcher actually owns the failing installation. No general claim that modern games use this file should be assumed.
Microsoft’s Visual Basic 6 documentation distinguishes the runtime files distributed with Windows from extended files delivered with the VB6 development media or redistributed by applications. Do not assume that every VB6-related file is part of the standard Windows runtime.
Microsoft’s VB6 security rollup, VB60SP6-KB926857-x86-ENU.msi, updates supported VB6 components, but it should not be treated as a guaranteed standalone repair package for addsccus.dll.
Fix 7: Use SFC and DISM only for broader Windows corruption
Because addsccus.dll is product-specific rather than a normal Windows system DLL, System File Checker will not normally recreate it. Use these tools when Windows itself shows wider problems, such as damaged built-in components, repeated system-service failures, or other corrupted system files.
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Run DISM first
- Open Start.
- Type
Command Prompt. - Right-click Command Prompt and select Run as administrator.
- Run:
DISM /Online /Cleanup-Image /RestoreHealth
- Wait for it to finish.
- Restart Windows.
Then run SFC
Open an elevated Command Prompt again and run:
sfc /scannow
Wait until verification reaches 100 percent, then restart and test the affected application.
These commands repair Windows component storage and protected system files. They do not replace a missing SourceSafe resource file or reinstall an old add-in.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 8: Update drivers only when the application shows a separate driver problem
A graphics, storage, chipset, or printer driver does not normally explain a missing SourceSafe resource DLL. Use Device Manager only if the same application also reports a hardware or driver failure.
- Right-click Start and select Device Manager.
- Expand the relevant category, such as Display adapters, Storage controllers, or Printers.
- Right-click the affected device.
- Select Update driver.
- Choose Search automatically for drivers.
- Restart Windows if an update is installed.
Do not uninstall an apparently unrelated device to fix addsccus.dll. If the error remains limited to the legacy application, return to repairing that application.
Outbyte Driver Updater can scan for outdated drivers instead of making you compare versions across many devices; the scan shows the findings, while driver installation is handled by the full version. Reinstalling the SourceSafe or host application remains the definitive fix when that application owns addsccus.dll.
Fix 9: Use System Restore only after a known change
System Restore is appropriate when the error began immediately after a known installation, update, or removal and a restore point predates that change.
- Press Windows key + R.
- Type
rstrui.exeand press Enter. - Select Next.
- Choose a restore point from before the problem began.
- Select Scan for affected programs if available.
- Review the programs and drivers that may be rolled back.
- Select Finish and allow Windows to restart.
System Restore rolls back system files, registry settings, and installed programs but does not remove personal files. It may not restore an application’s data or return a missing DLL if the product installation itself is incomplete.
If you no longer need SourceSafe
If the old source-control integration is abandoned, removing the request is safer than replacing the DLL.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problems- Back up any projects, source repositories, configuration files, and license records.
- Open Settings → Apps → Installed apps or Control Panel → Programs and Features.
- Uninstall the obsolete SourceSafe client, source-control add-in, or host application.
- Restart Windows.
- Disable obsolete startup entries and add-ins.
- Remove only shortcuts that point to the retired application.
If an active program still requests the file, do not delete registry entries blindly. Find the calling executable first, then repair or properly uninstall that application.
If the error persists after reinstalling
Check these points in order:
- Confirm that the repaired application is the same edition and architecture as the original.
- Verify that the SourceSafe client and host add-in were installed together.
- Check the application’s repair or installation log.
- Open Event Viewer by pressing Windows key + R, typing
eventvwr.msc, and pressing Enter. - Go to Windows Logs → Application.
- Look for an error at the time of the failed launch and note the executable, faulting module, and error code.
- Check for stale shortcuts, Office add-ins, scheduled tasks, or startup references.
- Determine whether the message is actually a dependency failure. “The specified module could not be found” can mean a dependency of
addsccus.dllis missing even when the file itself is present. - If the program is obsolete, disable the integration rather than repairing Windows globally.
Frequently asked questions
Is addsccus.dll a Windows system file?
No. It is a Microsoft SourceSafe add-in resource DLL associated with legacy SourceSafe, Visual Basic 6, and Access Developer source-control components.
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Which program installed it?
The strongest known association is Microsoft Visual SourceSafe. It can also appear with Visual Basic 6 tooling, Access Developer tools, or another application that bundled SourceSafe source-control integration.
Should I download addsccus.dll from a DLL website?
No. An untrusted download may contain malware, the wrong architecture, or an incompatible build. Use the original Microsoft media, a trusted organizational deployment package, or the owning application’s official installer.
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Should I reinstall Visual C++, DirectX, or .NET?
Not for this file alone. Reinstall those components only when the application separately identifies one of them as missing or damaged.
Should I register the DLL?
Usually not. addsccus.dll is a resource DLL, so regsvr32 is not an appropriate general repair method.
Does the file belong in System32 or SysWOW64?
There is no verified basis for placing it in either folder. A 32-bit application generally expects its application-specific DLLs in the product’s own installation directory.
What does “not designed to run on Windows” mean?
It is a generic Windows loader error family. Confirm the exact executable and installation involved before concluding that the DLL itself is invalid. Repair the matching legacy application and check for architecture or dependency problems.
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Will SFC or DISM restore it?
Normally no. They repair Windows components, while addsccus.dll belongs to a product-specific legacy installation.
What is the safest final answer?
Identify the program requesting the file, then repair or reinstall its SourceSafe, Visual Basic, Access Developer, or source-control component from trusted installation media. If the integration is no longer needed, uninstall or disable the obsolete component instead of placing an unknown DLL in a Windows directory.
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