It starts up in 'recovery' mode.
Just a blank screen with large white bars at the bottom. Then it says "Compaq" in big red letters, then I get a blue screen for using the recovery discs. There's 6 discs, but the computer keeps shutting down halfway through loading just one of them. (by shutting down, I literally mean the lights go out, the fan powers down and it turns off).
Then I press the big green button on the front of the computer and about half the time it'll turn back on long enough to go through the above process again. Or it'll keep shutting down and starting up.
Or I can press the button 50 times and nothing happens so I give up.
Hours later, it's turned itself back on again.

Basically, Windows is totally corrupt because of the multiple shutdowns so I'm trying to re-install the system software to bring it back to factory settings.
It won't stay on long enough to copy the files from the recovery CD's though.

I actually made it to disc #6 after about 10 hours of messing around... then it shut down and said to insert disc #1 again... so I had to start from scratch.