Can't be 100% sure what the problem is, but if you have a Windows XP CD handy, i may be able to help.
Put the CD in your computer, then restart it. Then go into BIOS options. BIOS can usually be accessed by pressing F8, but this varies by brand. if your not sure, then watch the screen as the computer boots. it will usually tell you what key to press. Once you get into BIOS, change your boot order so that the computer tries to boot from the CD-ROM first. Then save your settings and exit. your computer will restart. at this point you should get prompt asking you to press any key to boot from CD. Do so. Once setup loads, press the Enter key to setup windows, it will check for any previous installations. Now it SHOULD find your installation, but if not, then your out of luck. but if it does, press R to repair it. don't get worried, it will delete a few files at first, but this is a NON-DESTRUCTIVE way of reapiring Windows. Your account will remain untouched, all of your files will still be there. the only thing you will have to do in re-install your updates. If you don't have a XP CD, one can be downloaded off the internet. but this IS ILLEGAL
and therefore, i cannot give you any links. best of luck!
Edited by jnk1296, 10 February 2010 - 10:45 AM.