Quick answer: The error means a 32-bit application running under WOW64 (Windows-on-Windows 64-bit) triggered an internal assertion check and crashed. Find the exact app in Event Viewer (Application log, search for Warnings with source WER, then look for the process name), reinstall it, or update it to a 64-bit version. If it's a system file issue, run sfc /scannow.
What is ERROR_WOW_ASSERTION and why does it happen?
I remember the first time I saw this on a customer's Windows 10 machine — they were running an old accounting app from 2010. The error popped up as a vague message box with no app name. Frustrating as hell. Here's the deal: WOW64 is the translation layer that lets 32-bit x86 apps run on 64-bit Windows. When an app does something the translation layer can't handle — like a memory access violation or an invalid API call — the WOW64 subsystem throws an assertion error with code 0x0000029E. It's not a hardware problem, not a driver issue. It's almost always the app itself, or a corrupted DLL in SysWOW64.
Trigger examples: running a Visual Basic 6 app on Windows 11, using an old game that relies on DirectX 9 shaders, or launching a custom enterprise tool compiled for Windows XP. The error is nasty because it crashes the app instantly, often without a log entry in the Application event log unless you know where to look.
Step-by-step fix
- Find the exact app that crashed. Open Event Viewer (press Win + R, type
eventvwr.msc). Go to Windows Logs > Application. Click Filter Current Log... and set Event sources: WER, Application Error, or Windows Error Reporting. Look for events with IDs 1000 or 1001 within the last hour. The crashing module will be listed — for WOW64 issues, it might sayntdll.dllorwow64.dll. Note the app name and path. - If the app is from a vendor you trust, reinstall it. Uninstall the app from Settings > Apps > Apps & features. Reboot, then download the latest version from the vendor and run the installer as Administrator. Often an old installer left behind a mismatched 32-bit DLL in the app folder.
- Update the app to a 64-bit version if available. No joke — ask the developer. Many older tools have 64-bit builds now. If not, check for a compatibility patch. For example, my client's 2010 accounting app worked after they applied a hotfix from the vendor's support site.
- Run System File Checker to fix SysWOW64 corruption. Open Command Prompt as Administrator and type
sfc /scannow. Wait for it to finish. If it finds corrupted files but can't fix them, runDISM /Online /Cleanup-Image /RestoreHealthnext. - Test the app in a clean boot environment. Press Win + R, type
msconfig. Go to Services tab, check Hide all Microsoft services, then Disable all. Restart. If the app runs, a third-party service or startup program is interfering. Re-enable services one by one to find the offender.
Alternative fixes if the main steps fail
Use Compatibility Mode
Right-click the app's .exe file, go to Properties > Compatibility > Run this program in compatibility mode for Windows 7 or Windows XP (Service Pack 3). Also check Reduced color mode (8-bit or 16-bit) if the app is a game. I've seen this work for old VB6 apps on Windows 11.
Repair Visual C++ Redistributables
WOW64 assertion errors often trace back to missing or corrupted VC++ runtime DLLs. Go to Settings > Apps, find Microsoft Visual C++ Redistributable entries, and click Modify to repair each one. Or download the latest all-in-one from Microsoft's website.
Check for antivirus interference
Some security software hooks into 32-bit process creation and can trigger the assertion. Temporarily disable your antivirus (not Windows Defender) and try running the app. If it works, add the app folder to the antivirus exclusion list.
Prevention tips
- Always install the latest Windows quality updates. Microsoft patches WOW64 bugs regularly. I've seen KB5021233 (February 2023) fix this error for several users.
- Prefer 64-bit software. If a 64-bit version exists, use it. No WOW64 layer means no assertion errors.
- Keep a clean SysWOW64 folder. Don't manually copy DLLs into C:\Windows\SysWOW64. Use official installers.
- Test apps on a VM before deploying. If you manage enterprise software, spin up a Windows 10 or 11 VM and test 32-bit apps there. Catch the error before it hits production machines.
That's the full fix. No fluff, no magic — just practical steps that have worked for me and my team over hundreds of support tickets. If you're still stuck after trying these, the app might be too old for modern Windows. Consider virtualizing it with VirtualBox or using Windows 7 Mode (if you have Pro). But start with the steps above — they'll resolve 9 out of 10 cases.