Pci.sys.mui is considered a type of Dynamic Link Library (DLL) file. Dynamic Link Library files, like pci.sys.mui, are essentially a "guide book" that stores information and instructions for executable (EXE) files - like sapisvr.exe - to follow. These files were created so that multiple programs (eg. Windows) could share the same pci.sys.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 pci.sys.mui is attempted to be loaded either when Windows is starting up, or in some cases already running. Some of the most common pci.sys.mui errors include:
- Access Violation at address - pci.sys.mui.
- Pci.sys.mui could not be found.
- Cannot find C:\Windows\System32\drivers\en-US\pci.sys.mui.
- Cannot register pci.sys.mui.
- Cannot start Windows. A required component is missing: pci.sys.mui. Please install Windows again.
- Failed to load pci.sys.mui.
- The application has failed to start because pci.sys.mui was not found.
- The file pci.sys.mui is missing or corrupt.
- This application failed to start because pci.sys.mui was not found. Re-installing the application may fix this problem.
Your pci.sys.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, pci.sys.mui file corruption could be caused from a power outage when loading Windows, system crash while loading pci.sys.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.