hummm most comcraps I can think of use F10 to get into BIOS but you could also try unplugging the keyboard and see if it gives you an error message something like this "keyboard missing press F1 to continue with boot or F10 for setup" and if it does then you can turn it back off plug the keybaord back in and let it start up again and hit whatever key it told you to get into setup. or if you let us know what model the compaq is I am sure somebody here will have something like that sitting around that they could lookup the bios keystrokes. I think some people have had to use A VGA terminator on their video card to solve this problem like in this thread
http://www.mp3car.com/ubb/Forum2/HTML/001346.html so that might be what you will need to end up doing with it ?