What are CompatUI.dll.mui Error Messages?

Dynamic Link Library CompatUI.dll.mui Errors

CompatUI.dll.mui is considered a type of Dynamic Link Library (DLL) file. Dynamic Link Library files, like CompatUI.dll.mui, are essentially a "guide book" that stores information and instructions for executable (EXE) files - like _isdel.exe - to follow. These files were created so that multiple programs (eg. Windows) could share the same CompatUI.dll.mui file, saving valuable memory allocation, therefore making your computer run more efficiently.

Unfortunately, what makes DLL files so convenient and efficient, also makes them extremely vulnerable to problems. If something happens to a shared MUI file, either it goes missing or gets corrupted in some way, it can generate a "runtime" error message. Runtime is pretty self-explanatory; it means that these errors are triggered when CompatUI.dll.mui is attempted to be loaded either when Windows is starting up, or in some cases already running. Some of the most common CompatUI.dll.mui errors include:

• Access Violation at address - CompatUI.dll.mui.
• CompatUI.dll.mui could not be found.
• Cannot find C:\Windows\SysWOW64\en-US\CompatUI.dll.mui.
• Cannot register CompatUI.dll.mui.
• Cannot start Windows. A required component is missing: CompatUI.dll.mui. Please install Windows again.
• Failed to load CompatUI.dll.mui.
• The application has failed to start because CompatUI.dll.mui was not found.
• The file CompatUI.dll.mui is missing or corrupt.
• This application failed to start because CompatUI.dll.mui was not found. Re-installing the application may fix this problem.

Your CompatUI.dll.mui file could be missing due to accidental deletion, uninstalled as a shared file of another program (shared with Windows), or deleted by a malware infection. Furthermore, CompatUI.dll.mui file corruption could be caused from a power outage when loading Windows, system crash while loading CompatUI.dll.mui, bad sectors on your storage media (usually your primary hard drive), or quite commonly, a malware infection. Thus, it's critical to make sure your anti-virus is kept up-to-date and scanning regularly.

How to Fix CompatUI.dll.mui Errors in 3 Steps (Time to complete: ~5-15 minutes)

If you're encountering one of the error messages above, follow these troubleshooting steps to resolve your CompatUI.dll.mui issue. These troubleshooting steps are listed in the recommended order of execution.

To begin System Restore (Windows XP, Vista, 7, 8, and 10):

1. Hit the Windows Start button
2. When you see the search box, type "System Restore" and press "ENTER".
3. In the search results, find and click System Restore.
4. Please enter the administrator password (if applicable / prompted).
5. Follow the steps in the System Restore Wizard to choose a relevant restore point.
6. Restore your computer to that backup image.

If the Step 1 fails to resolve the CompatUI.dll.mui error, please proceed to the Step 2 below.

When the first two steps haven't solved your issue, it might be a good idea to run Windows Update. Many CompatUI.dll.mui error messages that are encountered can be contributed to an outdated Windows Operating System. To run Windows Update, please follow these easy steps:

1. Hit the Windows Start button
2. In the search box, type "Update" and press "ENTER".
3. In the Windows Update dialog box, click "Check for Updates" (or similar button depending on your Windows version)
4. If updates are available for download, click "Install Updates".
5. After the update is completed, restart your PC.

If Windows Update failed to resolve the CompatUI.dll.mui error message, please proceed to next step. Please note that this final step is recommended for advanced PC users only.

If Those Steps Fail: Download and Replace Your CompatUI.dll.mui File (Caution: Advanced)

If none of the previous three troubleshooting steps have resolved your issue, you can try a more aggressive approach (Note: Not recommended for amateur PC users) by downloading and replacing your appropriate CompatUI.dll.mui file version. We maintain a comprehensive database of 100% malware-free CompatUI.dll.mui files for every applicable version of Windows. Please follow the steps below to download and properly replace you file:

1. Locate your Windows operating system version in the list of below "Download CompatUI.dll.mui Files".
2. Click the appropriate "Download Now" button and download your Windows file version.
3. Copy the file into the appropriate directory for your Windows version:


Windows Vista: C:\Windows\System32\en-US\
Windows Vista: C:\Windows\SysWOW64\en-US\

4. Restart your computer.

If this final step has failed and you're still encountering the error, you're only remaining option is to do a clean installation of Windows Vista.

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