thanks for everyone's help! i was able to fix the problem by doing the following:
http://icrontic.com/...pair_windows_xp
However my laptop is working now but i was thinking that it would be a good idea to reinstall the windows files so that this doesn't happen again. Therefore please can someone tell me the easiest way i can reinstall the windows xp files only from the desktop (not by repairing windows or booting from the cd at startup). Thanks again