i assume you're running XP for your OS.... if that's the case, if you are able to get the computer to boot up properly, maybe using a different monitor, go into your system properties > advanced > startup & recovery settings, and uncheck the "automatically restart" under system failure. this will get rid of the quick restarts.
otherwise, you'll just have to stare at the blue screen and get as much info as possible (which may take a few restarts)...
as far as the problem goes... sounds like a drivers problem. did that monitor come with any installation disk?
p.s. i just went to HP's site to look for your drivers, and there doesn't appear to be any XP/2000 drivers available.... maybe the monitor didn't pass the XP compliance.
<a href="http://h20015.www2.hp.com/en/taskPageSelect.jhtml?reg=&plc=&lc=en&cc=us&prodId=compaqmv74217620&pagetype=software&docparent=software">drivers here</a>