That means the file system is corrupt and there may be bad sectors on the hard drive.
Try this:
1. Boot the computer with the Windows disc.
2. At the "Welcome to Setup" screen > press R to start the Recovery Console.
3. When prompted type "1". (if you have a multi-boot computer, select the installation you want to repair.)
4. When prompted > enter the Administrator password. If there is no password, just press ENTER.
5. Now you should be in the recovery console.
6. Type chkdsk c: /p /r > press <Enter>.
7. When the disk check is done: Type Exit > press <Enter>.
8. Take the Windows disc out and reboot.
If that doesn't work the hard drive has to be replaced.
