Since you have the Vista operating system, the steps are a bit different due to the UAC for running SFC. See the link below.
http://vistasupport.mvps.org/system_file_checker.htm

What SFC does is that it attempts to fix or replace critical operating system files. Sometimes this can be done without the installation disk, however it may prompt you for the appropriate operating system installation disk. If that is the case, then you know that you definitely have major file corruption or something missing. Insert the disk if prompted. Also you should run SFC using the Administrator account.

Don’t surf, play games or do anything while SFC runs. After it is completed, reboot your computer.

One of the major culprits in missing or corrupt operating system files is running a registry cleaner or optimizer. They can flag important shared files for deletion or cleanup. Another cause is malware.

NOTE: Before running any registry cleaner or editing the registry, always ensure you back it up first. If the registry cleaner you are using doesn’t have that function, you can do it manually. http://support.microsoft.com/kb/322756