pc restarts after shut down

[TONY11]

a couple of days ago thought i should clean the dust inside my pc. Disconnected all the wires power usb etc and opened the case to blow the dust from fans etc. When connected everything again started normaly but when i shut down the procces compleated normally and when done 2sec. later the pc restarted by itself and been doing it ever since. Any suggestions???

 

[Kage]

Hmm, this can occur when LAN cards etc are enabled after install somtimes, I've heard.
Did you by any chance reset the BIOS somehow to enable something that wasn't before?

Checked all power conections are in right and the right way?

 

[Tommy Boy]

Hmm...have you installed anything since then? Do you get any kind of errors when you shut down?

 

[TONY11]

everything was checked for connections correctly even uninstalled some upgrades which were sp2 and i only have sp1 and hoped that was it but nothing. Anything else before i reinstall windows or format AGAIN? please any suggestions will be apriciated. Thanks.