could cleaning a little dust really cause this?
Not directly but if you didn't discharge the static in your body before touching the inside of the case then you could have shorted the motherboard.
Is the system under warranty or is it a custom built?
You could try a inside case bench test and then if no results a outside case bench test would be needed. I am including the instructions below for you.
Disconnect everything from the Motherboard except
- video output
- 20+4 powercable
- 4/8 pin 12v wire both coming from the powersupply,
- Cpu fan wire
- power and reset button to the case
- case speaker
Now you should have NOTHING connected to the motherboard except what was listed above.
The goal here is just to test the mobo:
If the computer still will not boot up the please remove the motherboard from the computer along with the power supply
place the motherboard on a piece of card board larger than the motherboard,
this will eliminate a short from the mobo to the case which could be a possibility
Install the cpu with, 1 stick ram in dimm 1, power supply, case switch and case speaker
Connect ps2 mouse and keyboard along with the monitor
Repeat the above and power on
If the computer now boots into bios you most likely had a case short so make sure when installing the motherboard in the case that you use standoffs,
and they line up with the mounting holes in the motherboard and none of the standoffs touch anything else on the underside of the board.Thanks to Cbarnard for these instructions