Boot the PC using the XP CD and look for a prompt to 'Press any key to boot from CD' (some systems may not ask).
Press any key on the keyboard and Windows Setup will launch
After a few minutes you will be presented with the following choices:
To setup Windows® XP now. press Enter
To Repair a Windows® XP installation using Recovery Console, press R
To quit setup without installing XP, press F3
Press R to repair the Windows® XP installation
The next screen will ask you which Windows® installation you would like to log on to. Normally the following will be listed:
Press 1 and then Enter to continue.
You may now be asked for the Administrator password. If you know this type it and press Enter. If you don't know the Administrators password it may be blank. Just press Enter
At the command prompt type:
Chkdsk will now check the hard drive for errors, and will attempt to repair any it finds.
This process may take a while, but when finished will go back to the same command prompt as before.
Turn off and restart the computer.