* I have a working room with a common power switch for all the room. Every time I leave the room I switch the power off.
* In this room I have a Fujitsu Siemens computer running Windows XP.
When I switch the power on from the main switch, the computer starts, runs for 1-2 seconds, then it shuts down. After I push the computer's power button, it works normally, no more shuting down. I would guess the problem is the power supply. After about 1 year of these power on/off, the HDD collapsed.
* This glitch I saw on Dell and Fujitsu Siemens computers. ALL the computers I had of this brand had the same problem.
* Other brands (or piece by piece asembly computers of various brands) in the same room never had this problem.
* Resetting the BIOS didn't solved it.
I must add extra info as it appear that I didn't explained very well my problem. I had several computers (around 10 and not all of them were mine) of these two brands (OS installation or hardware fixing) and ALL of them had the same problems. At this moment I think the issue might be explained as Nick2253 suggested. Something like WOL or to power for various components. I will try to see if these settings can be changed by any motherboard jumpers or BIOS setup.
Plugging these computer in other sockets in other locations (friends houses) behaved the same.
Extra info about the setup:
* the computers don't have any PSU
* all the other equipments are working perfectly
* the power line is stable, no fluctuations, no powerloss