The Tool Desk
Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →If Windows reports that a0001726.dll is missing, was not found, or could not be loaded, do not start by downloading the DLL. The filename is associated with a legacy Internet Information Services component, and the correct repair depends on which application or server installation is requesting it.
Which fix applies to you
Use the description that best matches your situation:
As an Amazon Associate I earn from qualifying purchases.
- The error appears when starting a particular program: Repair or reinstall that program first. It may contain an old IIS dependency or a hard-coded reference to a legacy file.
- The error appears on a web server or after changing IIS: Check whether the site requires Server-Side Includes, then repair or reinstall the matching IIS feature.
- The problem began after an uninstall, update, cleanup tool, antivirus action, or migration: Repair the parent program, inspect quarantine history, and run Windows component repairs.
- The error says “The specified module could not be found”: A dependency of the named DLL may be missing. The DLL named in the message is not always the only problem.
- You are using Windows 10 or Windows 11 without IIS or server software: Do not install IIS just because the filename appears in an error. Identify the executable making the request first.
- The message appeared after a driver or hardware change: Check Windows Update and Device Manager, but treat the DLL error as an application or Windows-component problem unless the logs show a hardware-related cause.
The safest order is to identify the caller, repair the application or IIS installation, repair Windows, and only then investigate architecture or compatibility issues.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWhat a0001726.dll is
a0001726.dll is a real searchable filename associated with an older Microsoft IIS Server-Side Includes component. It is not a normal modern Windows redistributable that should be downloaded and copied into a system folder.
#1 Best Overall
Microsoft documentation identifies the older IIS Server-Side Includes interpreter as ssinc.dll. In IIS 6 and earlier, it handled Server-Side Includes in .stm, .shtm, and .shtml files. Microsoft’s current IIS documentation uses a different component name: ServerSideIncludeModule, implemented by iis_ssi.dll.
That distinction matters. Enabling Server-Side Includes on a current Windows installation may provide the modern IIS feature, but it may not create a file literally named a0001726.dll for an old application that requests that exact filename.
The reported filename is therefore best treated as a legacy IIS-related identifier. It may be legitimate in the context of an old server application, but it should not automatically be treated as a current Windows system file.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Step 1: Identify the program requesting the file
The DLL name alone is not enough to determine the repair. First find the executable, installer, or IIS site that is making the request.
Check the error window
Write down:
- The complete error text
- The title-bar name
- The program name shown in the message
- Whether the error appears during startup, installation, or when opening a website
- The folder path shown in the message, if one is provided
If the message names an application, repair that application before changing Windows features.
For example, an old server-management utility may need a legacy IIS component, while a desktop program may have incorrectly bundled or retained a server dependency. Installing IIS globally will not necessarily fix either situation.
Check Event Viewer
- Press Windows+R.
- Type
eventvwr.msc. - Press Enter.
- Expand Windows Logs.
- Check Application and System.
- Look for an event recorded at the same time as the DLL error.
- Open the event and note the Faulting application name, Application path, and Faulting module name.
If the event identifies a particular executable, repair or reinstall the package that owns that executable.
Check application and installer logs
If the error appears during installation or updating, cancel the installer and run the installer’s Repair, Modify, or Verify option if available. Look for a log entry containing a0001726.dll, ssinc.dll, iis_ssi.dll, or IIS-ServerSideIncludes.
Do not assume that a game or desktop application needs IIS simply because the error mentions a Microsoft DLL. The requesting executable is more useful evidence than the filename.
Fix 1: Repair or reinstall the application that reports the error
This is the most appropriate fix when one program displays the message.
Try the built-in repair option
- Press Windows+I to open Settings.
- Select Apps.
- Select Installed apps on Windows 11, or Apps & features on Windows 10.
- Find the program named in the error.
- Select the three-dot menu on Windows 11, or select the program on Windows 10.
- Choose Advanced options if available.
- Select Repair.
- Start the program again.
If there is no Repair option, open the program’s own installer or the classic Control Panel:
Free tools Windows power users keep installed
One-click scans. No signup required.
- Press Windows+R.
- Type
appwiz.cpl. - Press Enter.
- Select the affected program.
- Choose Change, Modify, or Repair.
The repair worked if the program opens without the missing-file message and its related feature functions normally.
Reinstall from the original source
If repair fails:
- Uninstall the affected program from Settings > Apps > Installed apps.
- Restart Windows.
- Reinstall the same supported program version from its original vendor or installation media.
- Restart again.
- Test the program before restoring custom settings or add-ons.
For a legacy server application, reinstall the matching IIS-era component from the same Windows generation or server installation media. A current IIS installation is not guaranteed to provide every file expected by older software.
If the program is no longer supported, the lasting fix may be to update its configuration, install a supported replacement, or run it on a properly maintained legacy server image rather than copying an isolated DLL into Windows.
Fix 2: Enable or repair IIS Server-Side Includes
Use this fix only when the affected website or server application actually requires Server-Side Includes.
Modern IIS exposes the feature as IIS-ServerSideIncludes. Microsoft’s Server Side Include setup documentation describes the relevant Windows feature paths.
Windows 10 and Windows 11 graphical steps
- Press Windows+R.
- Type
optionalfeatures. - Press Enter.
- Expand Internet Information Services.
- Expand World Wide Web Services.
- Expand Application Development Features.
- Select Server-Side Includes.
- Select OK.
- Allow Windows to install the feature.
- Restart the affected application or restart the computer if Windows requests it.
On some Windows editions, the feature may be shown under a slightly different IIS tree. Use the wording Server-Side Includes, not a similarly named scripting feature.
Windows Server steps
- Open Server Manager.
- Select Manage.
- Select Add Roles and Features.
- Continue to the Server Roles page.
- Expand Web Server (IIS).
- Expand Web Server.
- Expand Application Development.
- Select Server Side Includes.
- Complete the wizard.
- Restart the affected IIS site or application pool.
The feature is installed successfully when Server Manager reports completion and the IIS configuration recognizes the Server-Side Includes module.
Install the feature from an elevated Command Prompt
- Open Start.
- Type Command Prompt.
- Select Run as administrator.
- Run:
DISM /Online /Enable-Feature /FeatureName:IIS-ServerSideIncludes /All
- Wait for DISM to finish.
- Restart the application or server.
- Test the affected website.
To check the feature state, run:
DISM /Online /Get-FeatureInfo /FeatureName:IIS-ServerSideIncludes
Look for a state showing that the feature is enabled. Microsoft documents this feature name in its IIS installation instructions and explains the command format in its DISM Windows-features documentation.
Enabling this feature may resolve a current IIS configuration problem. It may not satisfy an old program that explicitly requests a0001726.dll or the older ssinc.dll name.
Fix 3: Repair Windows component files
Use Windows repair commands when:
- IIS feature installation fails
- Windows reports that protected files are damaged
- The problem began after a failed update or disk problem
- Several Windows components are failing
- The affected program is known to depend on Windows-installed IIS files
Run DISM, then SFC
- Open Start.
- Type Command Prompt.
- Select Run as administrator.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for the operation to complete. This may take time.
- Then run:
sfc /scannow
- Wait until verification reaches 100 percent.
- Restart Windows.
- Try the IIS feature installation or affected application again.
DISM repairs the Windows component store, while System File Checker checks protected Windows files. Microsoft describes this sequence in its Windows image repair guidance.
If DISM says that repair files cannot be found, connect the computer to the internet and run the command again. On managed computers, the repair source may be controlled by an administrator. You can also use a matching Windows installation source, but it must correspond to the installed Windows edition and build.
Do not replace the missing file with a DLL downloaded from an unrelated source.
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 problemsRepeating SFC and DISM without knowing what changed can make troubleshooting circular. If you want help identifying damaged Windows components while you work through these checks manually, Outbyte PC Repair can scan for reported issues; its free scan shows what it finds, while repair actions are handled by the full version. Reinstalling the application that specifically requests a0001726.dll remains the definitive fix for an application-owned dependency.
Fix 4: Check antivirus quarantine and security history
Security software can quarantine a DLL after an update, cleanup operation, or detection.
- Open Windows Security from the Start menu.
- Select Virus & threat protection.
- Select Protection history.
- Look for an event recorded when the error began.
- Check the affected program’s installation path.
- Do not restore the file solely because its name matches the error.
- If the detection appears valid or the file came from an unknown source, remove the program and reinstall it from trusted original media.
- Run a full scan after reinstalling.
Restore a quarantined file only when you have confirmed that it came from the original Microsoft or application installation, its digital signature is valid, and the security product’s detection is a false positive. If those facts cannot be established, reinstall the parent component instead.
Fix 5: Check architecture and legacy compatibility
Public metadata associated with this old filename reports a 32-bit file, but those details are not a current Microsoft catalog confirmation. Treat the architecture as an important compatibility question, not as permission to copy a file between system folders.
On 64-bit Windows:
System32is primarily the location for 64-bit system components.SysWOW64contains many 32-bit system components.- A 32-bit application may use Windows redirection to locate its 32-bit dependencies.
- Copying the same DLL into both folders does not repair missing dependencies, IIS configuration, or version mismatches.
Do not use a similarly named 64-bit DLL as a substitute for a 32-bit legacy component. Match the application, Windows generation, IIS generation, and component source.
If the program is old, check its documentation for supported Windows versions and required IIS roles. An application written for IIS 6 may not work correctly merely because the current IIS Server-Side Includes feature is enabled.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 6: Install Windows updates and check drivers only when the evidence points there
Windows Update can repair or replace supported Windows components.
- Open Settings.
- Select Windows Update.
- Select Check for updates.
- Install available updates.
- Restart Windows.
- Test the application again.
Drivers are not normally the cause of an IIS DLL lookup failure, but a driver or storage problem may be relevant if the error began alongside crashes, disk warnings, or hardware changes.
To check drivers:
- Right-click Start.
- Select Device Manager.
- Expand the device category related to the suspected hardware.
- Right-click the device.
- Select Properties.
- Open the Driver tab.
- Check the provider, date, and status.
- Use Update Driver only when a compatible driver is available through Windows Update or the hardware manufacturer.
Avoid replacing unrelated drivers merely because a DLL error exists. If manually checking every device and matching driver versions is taking time, Outbyte Driver Updater can scan for reported driver issues; its free scan identifies findings, while driver installation is handled by the full version. A driver update will not replace the correct repair or reinstallation of an application that owns the DLL reference.
Why regsvr32 is usually the wrong fix
Do not begin with:
regsvr32 a0001726.dll
IIS components are normally installed and configured through IIS roles, features, modules, and handler mappings. They are not automatically repaired by registering a DLL as a COM component.
If the file does not expose the required registration entry point, regsvr32 may report that DllRegisterServer was not found. Even if registration succeeds for another DLL, it would not recreate the required IIS configuration or restore a missing dependency.
Use regsvr32 only when the software vendor or Microsoft documentation specifically identifies a self-registering DLL and provides the appropriate registration procedure.
Recommended Free Tools
Why random DLL downloads are unsafe
Downloading a0001726.dll from a file archive is not a reliable repair because you cannot safely establish that the file matches:
- Your Windows edition and build
- The original IIS generation
- The application’s required architecture
- The correct language and dependencies
- The expected digital signature
- The security state of the computer
A replacement can also hide the real problem, such as a damaged component store, incomplete application installation, stale configuration, or malware. Do not copy an arbitrary DLL into System32 or SysWOW64.
Use Windows Features, Windows Update, Microsoft repair commands, the original application installer, or verified installation media instead.
Best Value
If the error still appears
After completing the appropriate repair:
- Restart Windows.
- Open the application or website again.
- Record the full error text.
- Note the executable path shown in Event Viewer.
- Check whether the error occurs for every user or only one profile.
- Review the application’s logs for a hard-coded reference.
- Use Process Monitor only if you are comfortable filtering file activity by the requesting executable.
- Look for attempts to open
a0001726.dll,ssinc.dll, oriis_ssi.dll. - Repair the component that owns the request.
If modern IIS is installed and working but the same program still requests a0001726.dll, the application may contain a stale legacy reference. In that case, enabling more IIS features or copying files will not be a dependable solution. Update, reconfigure, or replace the application.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →FAQ
Is a0001726.dll a legitimate Windows file?
It is a legitimate searchable filename associated with a legacy Microsoft IIS Server-Side Includes component. It is not the normal filename used by current IIS documentation, so verify the requesting program before treating it as a current Windows system file.
Does a0001726.dll belong to Windows 10 or Windows 11?
There is no established evidence that Windows 10 or Windows 11 ships this exact filename as a standard current system file. Modern IIS uses iis_ssi.dll for its Server-Side Includes module.
Should I enable IIS to fix the error?
Only if the affected application or website requires IIS. If a desktop application alone reports the error, repair that application first. Installing IIS may not provide the exact legacy filename it requests.
Is the file 32-bit or 64-bit?
Publicly indexed metadata reports a 32-bit legacy file, but this is not a current Microsoft catalog confirmation. Do not copy files between System32 and SysWOW64 as a generic fix.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallCrashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteCan I run regsvr32 on it?
Usually no. IIS feature installation and configuration are the relevant mechanisms. regsvr32 does not restore IIS mappings or missing dependencies.
What does “the specified module could not be found” mean?
It can mean that a dependency of the named DLL is missing. The named file may exist while another required module cannot be loaded.
Where should I get the replacement file?
Do not download an isolated replacement. Repair Windows through Microsoft’s supported tools, reinstall the original application, or restore the matching IIS component from verified installation media.
What if antivirus removed the file?
Check quarantine and event history. Restore only a verified original file when its signature and source are clear. Otherwise scan the computer and reinstall the parent application or IIS component.
