The System File Checker (SFC) is a utility in Windows that allows users to scan for corruptions in Windows system files and restore corrupted files. It can be used to fix DLL errors by scanning the system for any missing or corrupted DLLs, and replacing them with the correct versions. This can help to resolve many common DLL errors, such as missing DLLs, corrupted DLLs, or incorrect versions of DLLs.