What I have done so far:
- start the pc --> nothing, only small light on front of casing, no mouse, no keyboard, no beep
- opened up the casing (removed dust). start the pc --> 2x fans running nothing else, only small light on front of casing, no mouse, no keyboard, no beep
- inserted the Windows 7 CD, start the pc --> nothing, only small light on front of casing, no mouse, no keyboard, no beep
- unplugged the power, removed the video card, removed the 3V battery, checked the voltage (over 3V), reinstalled battery, video card, power --> nothing, only small light on front of casing, no mouse, no keyboard, no beep
- unplugged the hardddrive, opened up a Dell computer I have lying around, connected the hard drive, started that pc --> beep, nothing else. Can't connect monitor a it is a different connector.
- tried the hard drive from the Dell pc in my normal pc --> nothing at all. But I might have had one small 4-pin connector on the motherboard still disconnected.
Tried delete, F2, F12 yesterday, but as I don't have keyboard function --> nothing