Thanks for all your helpful adivce and suggestions!
Okay, this is the current situation:
- I press ON button on PC
- Power green LED starts blinking, in intervals of about twice every second (so once every 0.5-seconds)
- fan turns on
- nothing else happens - there is no output on the monitor, etc.
- the only way to shut it off is to kill the power to the PC (flip off the switch at the back)
Any other ideas? There are no sounds, etc. coming from the PC. Also, the HD light doesn't turn on. Only the power LED turns on.