I hope you have your Windows CD.
If so, please do as follows:
Please go to Start -> Run -> type cmd and press Enter.
At the command prompt, type sfc /scannow, making sure to put a space between the "c" and the slash, and then press Enter. This will run the System File Checker.
Follow the prompts, and insert your Windows installation CD if requested. Then please restart your computer.
See if there is any difference.