The exact aswmonvd.dll errors
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsYou may see this message when opening a DOS program, launching command.com, or starting Windows:
16 bit Windows Subsystem: C:Program FilesAlwil SoftwareAvast4aswMonVd.dll. An installable Virtual Device Driver failed Dll initialization. Choose 'Close' to terminate the application.
Other possible loader messages include “aswmonvd.dll is missing,” “Error loading aswmonvd.dll,” or “The specified module could not be found.” These generic messages do not prove that the file is a current Windows component.
The 60-second answer
aswmonvd.dll belongs to legacy Avast antivirus installations, particularly Avast 4 and its former Alwil Software directory. It is not a Windows system DLL, Microsoft runtime, DirectX file, game dependency, or normal modern Avast component.
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Do not download a replacement DLL or copy one into System32, SysWOW64, or an application folder. The most likely cause is either a damaged old Avast installation or a stale reference left behind after Avast was removed.
Use this order:
- Repair Avast if it is still installed.
- Run Avast’s official uninstall utility if Avast was removed or repair fails.
- Check whether the error appears only with a DOS or 16-bit application.
- Remove a stale legacy reference only if the official cleanup does not resolve it.
- Use Windows repair commands only when other Windows components are also failing.
Why Windows reports this file
Historical Avast installations used aswMonVd.dll as an installable virtual device driver for the Windows 16-bit and MS-DOS subsystem. That is why the message may mention an “installable Virtual Device Driver” instead of simply reporting a missing DLL.
The old Avast path commonly shown in reports is:
C:Program FilesAlwil SoftwareAvast4aswMonVd.dll
The capitalization in the displayed path can vary. The important clues are the Avast 4 directory and the fact that the error appears while starting a DOS-based program.
A startup error after uninstalling Avast usually means Windows still has an old reference to the file. Removing the file alone does not remove every registry or startup configuration entry that referred to it.
There is no reliable current version, publisher record, supported 64-bit release, or consistent public hash that can be used to validate a downloaded copy. Treat file-index metadata as unreliable for this obsolete component.
Fix 1: Repair Avast if it is still installed
This is the correct first step when Avast remains on the computer and you want to keep it.
- Press Windows + I to open Settings.
- Select Apps.
- Select Installed apps on Windows 11, or Apps & features on Windows 10.
- Find Avast Free Antivirus or Avast Premium Security.
- Select the three-dot menu beside it.
- Choose Uninstall.
- When Avast Setup opens, choose Repair rather than removing the product.
- Confirm the repair and wait for Setup to finish.
- Restart Windows if Avast requests it.
After restarting, launch the program that produced the error. If the message no longer appears, the Avast installation or its legacy configuration was damaged.
If Avast Setup does not open, the repair option is unavailable, or the repair fails, continue with the removal procedure below. Do not try to repair the installation by downloading aswmonvd.dll separately.
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Fix 2: Remove incomplete Avast software with Avast’s utility
Use this path when Avast was already uninstalled, the error began after an uninstall, or the Avast installation is too damaged to repair.
Download avastclear.exe only from the official Avast Support website. Then:
- Save the utility to a location you can find easily, such as the Desktop.
- Right-click
avastclear.exe. - Select Run as administrator.
- Accept the Windows permission prompt.
- Allow the utility to reboot Windows into Safe Mode when prompted.
- In Avast Clear, confirm the detected Avast installation folder.
- Choose Remove.
- Use Remove & Reinstall only when you specifically intend to install Avast again.
- Let the cleanup complete.
- Restart Windows normally.
For an old Avast 18.8 installation on Windows XP, Avast documents a separate XP-compatible uninstall utility. Use the utility intended for that legacy operating system rather than assuming the current removal tool supports it.
Test the computer after the restart. If the message appeared during normal startup and is now gone, the problem was a leftover Avast component. If it appears only when opening a DOS program, check the compatibility issue in Fix 4.
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Fix 3: Check for a stale VirtualDeviceDrivers reference
This is an advanced step for a legacy Windows installation. Avast’s official cleanup utility is safer and should be attempted first.
The historical registry location is:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlVirtualDeviceDrivers
Older reports also refer to ControlSet001 and ControlSet002.
Before changing anything:
- Press Windows + R.
- Type
regedit. - Press Enter.
- Select Yes if User Account Control appears.
- In Registry Editor, select File → Export.
- Choose All under Export range.
- Save the backup to a removable drive or another safe location.
Then inspect the key:
- Browse to
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlVirtualDeviceDrivers. - Look for a value that contains an old Avast 4 path or
aswmonvd.dll. - Do not delete the entire key.
- If the obsolete Avast entry is clearly identified, remove only that entry.
- Close Registry Editor.
- Restart Windows and test the affected program.
Do not perform this edit if you are unsure which value belongs to Avast. Deleting the wrong value can affect DOS compatibility. On newer Windows versions, this registry path may not exist or may not be the cause at all.
If the error dialog shows a different file path, investigate that exact path instead. A persistent startup message may refer to another old antivirus component rather than aswmonvd.dll.
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Fix 4: Check whether the program is 16-bit
If the message appears only when launching an old DOS or 16-bit Windows application, the missing Avast reference may not be the only issue.
Microsoft states that NTVDM and 16-bit application support are available only on x86 editions of Windows. Windows x64 and ARM do not provide the same NTVDM support. Installing a DLL cannot add 16-bit support to a 64-bit operating system.
Check your architecture:
- Press Windows + I.
- Open System → About.
- Find System type.
- Note whether Windows is x86, x64, or ARM-based.
On x64 or ARM Windows, use one of these approaches:
- Find a modern 32-bit or 64-bit replacement for the application.
- Run the software inside a compatible x86 Windows environment.
- Use a virtual machine configured with an operating system that supports the program.
- Ask the software vendor whether an updated build exists.
Do not install NTVDM as a fix on x64 Windows. Microsoft’s compatibility documentation explains the architecture limitation in its NTVDM and 16-bit app support guidance.
If you are using x86 Windows and the application previously worked, complete the Avast cleanup first. The error may be a stale Avast virtual-driver reference rather than a fundamental Windows incompatibility.
Fix 5: Remove conflicting legacy antivirus components
Historical cases involved old Avast and Norton or Symantec components being present together. Multiple leftover antivirus drivers can interfere with startup and with older DOS compatibility components.
- Open Settings → Apps → Installed apps.
- Remove antivirus products you no longer use.
- For each product, use its vendor’s official cleanup utility if the normal uninstall leaves errors.
- Restart after the cleanup.
- Keep only one real-time antivirus product active.
Do not manually delete antivirus driver files from Windows directories. Security software often has services, drivers, scheduled tasks, and registry settings that must be removed together.
Fix 6: Repair broader Windows corruption
SFC normally does not restore aswmonvd.dll because the file is associated with third-party Avast software, not protected Windows components. Use these commands when Windows has additional symptoms, such as damaged system tools, repeated component errors, or unrelated built-in applications failing.
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- Open Start.
- Type Command Prompt.
- Right-click Command Prompt.
- Select Run as administrator.
- Run:
DISM.exe /Online /Cleanup-image /Restorehealth
- Wait for it to finish.
- Then run:
sfc /scannow
- Restart Windows.
Microsoft recommends running DISM before SFC. The command details are available in Microsoft’s System File Checker guidance.
Running these commands repeatedly will not recreate a deleted Avast installation. If they report that Windows repaired files but the Avast message remains, return to the Avast repair or removal steps.
When manually hunting through component versions and repeating DISM or SFC without knowing what changed becomes impractical, Outbyte PC Repair can scan for issues and show what needs attention; its free scan identifies problems, while repair is handled by the full version, and reinstalling Avast remains the definitive fix for this file.
Fix 7: Update or reinstall drivers only when the symptoms point there
A normal display, chipset, storage, or audio driver is not a likely source of aswmonvd.dll. Consider driver work only if Device Manager shows an error, Windows has hardware instability, or the problem began with a broader driver failure.
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- Select Device Manager.
- Expand the category for the affected hardware.
- Right-click the device with a warning icon.
- Choose Update driver.
- Select Search automatically for drivers.
- Restart Windows if a driver is installed.
For a damaged device entry:
- Open Device Manager.
- Right-click the affected device.
- Select Uninstall device.
- Confirm the removal.
- Restart Windows.
- Install the replacement driver from the hardware manufacturer if Windows does not restore it.
Do not expect this to restore Avast’s old virtual-driver configuration. When identifying which of dozens of hardware drivers is stale is the difficult part, Outbyte Driver Updater can scan and identify outdated drivers; its free scan shows the findings, while driver installation is handled by the full version.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why regsvr32 usually does not help
Do not run:
regsvr32 aswmonvd.dll
as a generic repair command. regsvr32 is intended for DLLs that provide registration entry points such as DllRegisterServer. aswmonvd.dll is historically described as a virtual device driver, not as a self-registering COM or ActiveX component.
You may receive an entry-point error, or the command may appear to complete without restoring the missing Avast configuration. Microsoft explains the command’s purpose and limitations in its regsvr32 documentation.
A 32-bit DLL also cannot be made valid for a 64-bit process by renaming it or moving it between System32 and SysWOW64.
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A DLL archive cannot reproduce the Avast installation that originally used this file. It may provide the wrong architecture, an incompatible build, altered metadata, or a file that does not belong to Avast at all. Public listings for this obsolete DLL disagree about basic file information, so a listed hash or size is not a trustworthy repair basis.
Copying a file into a Windows directory can also hide one dialog while leaving the stale registry reference intact. Use the official Avast installer or Avast’s official uninstall utility instead. If the old program itself is no longer compatible with your Windows architecture, replace it or run it in a suitable virtual machine.
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FAQ
Is aswmonvd.dll a Windows file?
No. Available historical evidence associates it with legacy Avast and Alwil Software installations. It is not a standard Windows system component.
Is it part of modern Avast?
There is no reliable evidence that it is a normal file in current Avast releases. The strongest references point to Avast 4 and legacy 16-bit support.
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Should I restore it from antivirus quarantine?
Only if the file came from a verified Avast installation and Avast Support confirms that restoration is appropriate. Do not restore an unknown copy or download a replacement.
Does SFC fix aswmonvd.dll?
Usually not. SFC repairs protected Windows files, while this DLL is associated with third-party Avast software. Run SFC only when broader Windows corruption is suspected.
Why did the error start after uninstalling Avast?
The DLL may have been deleted while an old VirtualDeviceDrivers or startup reference remained. Avast’s official removal utility is safer than manually rebuilding the missing file.
Can Windows 11 run the old DOS program?
Windows 11 on x64 or ARM cannot use NTVDM for 16-bit applications. Use a modern replacement, an x86 Windows environment, or a virtual machine.
What if the error remains after Avast is removed?
Read the complete path in the dialog. It may point to another obsolete antivirus DLL or a different application. If the path still names Avast, repeat the official cleanup and inspect the legacy registry reference only with a verified backup.
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