Computer Problems - PLEASE READ

Let me start a while back. My computer has a difficult time booting up usually.... I'll start it, but nothing happens. The second or third time, usually (more if I have recently moved the computer it seems), I get the "everything is okay" beep, and the computer starts.

Current Problem:
Originated about a week ago.

My computer just shut off... The fans were still spinning, the lights on the hardware was still on, but the monitor was black. The light on the monitor blinked insinuating no input. The fans sounded a bit different I think.

I turned it off (as the power was still running... just no picture or sound), and turned it back on. It stayed on about 5 seconds. I repeated, and it lasted about 10 seconds. I repeated twice, and I got to the logon screen both times.

I took the side panel off the computer... Maybe a heat problem? It booted and stayed on.

The temperature gauge never went about 24C I think, and usually, it was around 20. Because of this, I mentally ruled out temperature problem as the fan previously indicated.

Yesterday, while playing a flash game, my computer did the same thing. The monitor lost signal, the sound went out, and the fans may have sounded a bit different (This may just have been me actually listening to them though...).

I rebooted several times, and I've only gotten about 15 seconds of activity before it goes into hibernation.

Panel on, panel off, blow out dirt, test connections on everything... I don't know what else to do. Anyone have a suggestion, diagnosis, or a guess as to what may be causing the problem? (It's not a virus. Norton and antivirus.com both confirm that.) If you don't know, but you know someone who might, please ask them... This is really important to me...

Thanks.