Actually if the repair doesn't work you'll want to access the Recovery Consule.
When the Recovery Consule gets to a DOS prompt you'll need to select the the
OS to be recovered, usually 1 and hit enter. It will then want the Administrator Password. Type it in and hit enter. You should be at C:\Windows
Now type chkdsk c: /r and hit enter. This process can take quite some time to complete and it may or may not fix it. But I've had success in recovering corrupted system files in the past.
Good Luck