I realise that I already have a topic regarding a motherboard, which powers on the cpu fan for 3 seconds, then turns off. This is a different machine, and a different problem. In this case, the cpu cooler works fine, but I get no image on my monitor. I have already tested the monitor, and verified that it is not the problem.
The motherboard is a Asrock ALiveNF6G-VSTA. The problem occured after the computer being accidently dropped on the floor. I have tryed booting with only one ram stick. Still same problem. The motherboard has on-board graphichs, so I have tested on the onboard graphics, altough I tried inserting a video card - the fan on it started spinning, but no video appeared on the monitor. I have also tryed installing another PSU, with the same result.