onion

Ok, so I have a XFX geforce gtx 260 Black Edition, while its in the pc it basically won't allow my computer to boot, absolutely nothing comes up on the screen, most of the time, no motherboard tones or anything, once in a while you might get 10 motherboard tones, which should be the cmos right?.But, the computer will boot just fine with a different graphics card (Geforce GT 430) installed, I've tried various things, such as making sure the aux power connectors are properly connected, all the motherboard connections etc, still the PC refuses to boot with this video card installed. The video card is free off dust (as I've cleaned it recently, so it isn't over heating. When it was working (a few days ago) it used to stay at around 70 degrees c while it was running a game. I'm beginning to assume the video card is just dead, but this seems like a very odd fault, so if you have any ideas at all what could be causing this, give me advice, thanks in advance