To orty84,
When you have something that dead---you have to have some tools in your toolbox to narrow things down---or it could be anything---which is an impossibly wide universe to troubleshoot.
You could start out with a dos boot disk---on a floppy or a cd---can you log onto a cd drive or a floppy?--can you then log onto the hard drive?--whats on the hard drive?---something like memtest86 will test memory for errors---having something like a knoppix cd would be even better and would let you see if linux loads--and maybe narrow things to the C drive.
And human beatbox is also right---find your mobo # and download the manual. And if you can get into the bios---you can start getting clues---and one other thing---if this computer has been joosled around in shipping, open the case and see if boards or connectors have jarred loose.
Sometimes you find your problem by elimination---and you look at the things the computer can do to find what it can't do.
But you are going to have to post a lot more detail before anyone here or anywhere can help you troubleshoot.