Sometimes, installing third party software in Windows XP can overwrite important system files and lead to instability. This is where an under-used part of the Windows XP operating system comes into its own.

System File Checker (sfc.exe)

Running this utility couldn't be easier. All you need to do is;

Go to the Run box on the Start Menu and type in:

sfc /scannow ( sfc if not reconized) (Note that there is a space between sfc and /scannow)

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


In all likelihood you will be prompted to insert the Windows CD.
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If your using Vista follow these instructions:

Click Start/ All Programs/ Accessories
Right click on the Command Prompt option, on the drop down menu which appears, click on the Run as Administrator option

If you haven’t disabled User Account Control (and you shouldn’t!) you will be asked for authorisation. Click the Continue button if you are the administrator or insert the administrator password.

Start the System File Checker

In the Command Prompt window, type: sfc /scannow, press Enter
You’ll see “the system scan will begin”.

The scan may take some time and windows will repair/replace any corrupt or missing files. You will be asked to insert your Vista DVD if it’s needed.

Close the Command Prompt Window when the job is finished.

One caveat: you need a Windows CD or DVD to enable SFC to make repairs.

http://support.microsoft.com/kb/929833/en-us

If you start the process without the CD/DVD and you are constantly prompted by the process, simply do the following;

Go to Start> Run > and type: sfc /revert : Click ok or hit enter key and reboot. This will stop all sfc functions...