Another 'My computer will not turn on thread'

Hi guys,

My girlfriends brother has come in drunk and decided to turn his computer off at the wall, when he turned it back on it said boot from windows or launch the restore wizard or something along those lines. His USB keyboard wasn't recognised at boot so he couldn't select either option.

I got a keyboard with a ps/2 connection from the cupboard and plugged it into the back of his machine, now however when you turn on the system nothing happens, no display, no beeps and no HD activity.

Anyone got any ideas where to go from here? checked the motherboard and apart from lots of dust everything seems connected and is fine.

Cheers.