Hi, welcome to TSF.
Run Windows chkdsk on the C: drive:
Start the computer with the Windows CD.
At the
Welcome to Setup screen, press
R to select the repair option.
You will have to enter the Administrator password - if none, just press <Enter>.
At the command prompt - type
chkdsk c: /r > press <Enter>. (note the space after c:)
When the disk check is done:
Type
Exit > press <Enter>.
Take the Windows disc out and reboot.
Also - please post a screenshot of Disk management.
How to post a screenshot.