I find this tool to be most useful after a malware infection. I always run it in this case just to make sure important Windows system files are intact. Of course, the only way to be completely sure you have a clean system after an infection is to re-install the OS. The SFC tool is also useful for cleaning up broken system files that have resulted from some kind of disk corruption.
These commands will work on all OSs, XP and newer.
Run a full verification & replacement scan
1. Open a command prompt
Run a full verification scan
Scan and replace a single file
Verify a single file without replacing it
See the following sites for more information on this tool and how to use it: