Can a mobo work with a busted pci express slot?

[Taget]

My pc refused to start a month or so ago, I took out the BFG 8800 gt I had in the pci express slot. I didn't have another pci express card to replace it with so I put in a old TNT2 pci card in one of the old pci slots and the system worked fine. I thought well its got to be the 8800gt then and sent it back to BFG because it was still under warranty. Today I got the parcel back from BFG and was pleased to see they had given me a 9800 GTX+, I went and put it in but again the pc wouldn't boot just like with the 8800gt I had. This made me think that it must be the pci express slot itself because it works fine using a old pci TNT2 card. But I would have thought that if the pci express slot was broken the pc would at least say something in the bios? I suppose there is a chance that the 9800 GTX+ they sent me is a dud to but I doubt it. Anyone have any ideas? Any help is much appreciated because I want to install Win 7 and play my games that the TNT2 won't stand a chance of running. Thanks

Specs: AMD 4200+, Asus A8Ne, 2gb DDR, 9800 gtx+(in pci express/TNT2(in pci), 500w power supply with 36amp on 12v.

 

[Monkeynut]

Can you try the 9800GTX+ in another machine? What brand is the PSU?

 

[Taget]

All the other desktops in my house are AGP. I could take it into a shop and get them to test it sometime. I'm wondering if a mobo would even start if the pci express was broken and if it did sureley there would be some sort of notification on the post, in the Bios or in device manager. But it says on the card they sent me that its been tested to. I can't believe they would send me a dud 9800gtx+ to replace my 8800gt, I was so pleased at first to because I got a better card than the one I sent back.

 

[Taget]

Mind you saying that if it was just the mobo's pci express slot they wouldn't of replaced my 8800gt if it was working would they?