PCI cards not detected.

I've got a GeForce 6100 "SM-M" motherboard and its psu broke a while ago, it was just still under guarentee so I sent it back. Now with the returned computer (and an expired guarentee) none of my PCI cards can be found. I've got a sound card, a tv and a 6series graphics card, al of which used to work, and now, even with drivers installed nothing. I've tried one of the cards on my mates pc, and that worked fine. I really dont know much about hardware, but is the psu supposed to connect directly to the pci ports? or is the reason there not detected beacuse my motherboards #!@$%£?