How to Repair DLLs in Microsoft Windows

Background
DLL (Dynamic Link Library) files contain commonly used data and code that is accessed by various application programs as well as the operating system itself. Microsoft Windows makes extensive use of DLL files to perform its various functions efficiently. If these DLL files become corrupted, they can cause errors and problems on your PC.
Repair
The System File Checker program checks important system files, including operating-system DLLs, and replaces any files it finds to be corrupt with the original versions. It is likely you will be prompted to insert your original operating-system CD or DVD in the event of the program's finding any corrupt files.
Operation
Microsoft provides instructions on how to use the SFC program. It is necessary to run the program from the Command Prompt interface, which is accessible via the Windows Start menu.