Pci-to-Pci Bridge (Error: Code 10) - PCI Video Card

I'm running Windows 7 Enterprise 64-bit edition, not the Beta or RC. I have 3 video cards in my possession (listed below).

- (PCIe) Evga GTX260
- (PCI) Evga 9400GT
- (PCI) Evga Fx5500

Out of those 3 cards I only use the GTX260 and the 9400GT. I had to 'retire' the Fx5500 because the latest WHQL (certified) drivers only provide support as far down as the "6 series" Nvidia cards. Unfortunately the Fx5500 is a "5 series" and falls below that line. I have already tried to use the GTX260 and Fx5500 in previous versions of Windows (XP and Vista), but there is no way to download and install two separate drivers for two of the same make of video card - you'll get nothing but errors.

There is the option of going to a place like guru3d.com and downloading a custom supported driver that covers both the GTX260 and Fx5500, but the drivers are not certified and lack support. Therefore, I purchased and now use the 9400GT which is covered under the drivers for the GTX260 and eliminates the need for messing around with custom drivers. Also, the 9400GT has a better graphics processor and more memory than the Fx5500, so it was time to upgrade anyway.