System File Checker
System File Checker is a Microsoft utility to scan and restore corruptions in Windows system files(availble from Windows 98 onwards).
Open an elevated command prompt
System File Checker tool in Windows 98
Click Start, point to Programs, point to Accessories, point to System Tools, click System Information, and then click System File Checker on the Tools menu.
Click one of the following options:
Scan For Altered Files
Extract One File From Installation Disk
Click Settings, choose the configuration you want to use in System File Checker Settings, click OK, and then click Start.