Nicdez...I'd like to have you run this first:
Click Start then Run...type sfc /scannow (Note the space between sfc and /) and press "Enter". You will be asked for your installation cd, so have it handy. Wait for the scan to finish (this might take up to an hour). When it's finished, click Start then Run...type chkdsk /r /f (Again...note the spaces) and reboot when prompted. This will run on boot-up so restart will take a while...be patient.
Please post back with your results....