Motherboard issues or psu?

[imported_nrosario]

I have:
Asus P5AD2 Premium motherboard
Antec NeoPower 480 power supply

I was doing some maintenance on my computer, cleaning etc
When I hooked everything back up, the computer refused to boot.
Also my motherboard light fades out, and then my computer emits a buzzing noise

None of the fans are working, HD lights, Mobo Lights, nothing
Is my PSU dead?

 

[IGBT]

..reseat all your connections and try again. something may be poorly seated or loose.