hi,,, just to follow on from JosiahK's reply,,, if you have the windows disc or recovery disc then with this disc in the drive try a system file check,,,
1. Click the Windows button>> All Programs>> Accessories.
2. Right click the Command Prompt option and then select "Run as administrator" from the resulting menu.
3. With the Command Prompt window showing, type in: sfc /scannow [Enter]
4. You will now receive a message that states the scan will now begin. If SFC should find any rogue files that need to be replaced, you may be asked to insert your Windows CD. If the SFC scans without finding any problems, you will receive the following message: "Windows resource protection did not find any integrity violations".
5. Close the command prompt window.
if this fails to find and fix the issue then also with the windows/recovery disc run a startup repair of the os on the pc,,, you will need to boot from said disc for this one,,, full instructions in the link below http://www.bleepingcomputer.com/tutorials/repair-windows-with-windows-startup-repair/