What exactly happens when you try to boot the computer? Has it completely died, or do you get some sort of message? Yes, do try to boot from dos, to see what is left of your configuration. One note: if you -do- get it back up and running, yank out the network / modem cable until you found out how he got in. My best guess is that he used some sort of trojan: install a virus scanner, and perform a complete system scan first thing when you get it back up again.