The main reason for using this utility is when you suspect there may be a problem with a Windows XP system file.
Perhaps you get a dialog box appear informing you of a problem with a .dll file, or your program will just not load! It is therefore worth checking to see if there are any corrupt system files using scannow sfc.


To do this simply go to the Run box on the Start Menu and type in:

sfc /scannow

This command will immediately start the Windows File Protection service to scan all protected files and verify their integrity, replacing any files with which it finds a problem.



There are a few other sfc functions as well:
sfc /scannow - Scans all protected system files immediately.
sfc /scanonce - Scans all protected system files once.
sfc /scanboot - Scans all protected system files every time the computer is restarted.
sfc /revert - Returns the scan to its default operation.

If you have multiple drives and partitions, this tip to the tutorial may be of help.

When you install Windows from a CD that has had a Service Pack slipstreamed into the installation files, when you run Windows File Protection's DOS commands, such as "sfc /scannow" it requests the original CD.

You insert the CD used to setup Windows but instead of accepting that disk, it repeatedly requests that you "Insert your Windows XP Professional Service Pack 2" CD.

In my case, the solution was to change the value in the "SourcePath" key in my registry showed "D:" which is the drive letter that was in effect for my primary CD-ROM drive during install.


However, since install I have changed the drive letter for several devices, including the CD-ROM drive. Once I changed "D:" to "H:", SFC /SCANNOW worked fine.

Apparently, SFC/WFP looks at the registry to see if the SourcePath matches, instead of actually LOOKING at the CD's contents to verify validity.

Remember to backup your registry before making changes to it...