Mac Pro 1st Gen Graphics Card Question I have just inherited a first-gen Mac Pro, however it comes with no power supply, no CPUs and a 7300GT graphics card.

My questions are:

1 - I know OS X needs an Apple graphics card to boot, is it possible to put the 7300GT in one of the slower PCI-Express lanes and put a PC graphics card in lane 1 (the x16 lane) and still have it boot? If not, what are my options? I intend to use the PC card only when booting to Windows.

2 - Power supply - Are there any PC PSUs that will work with this? What are my cheapest options?

3 - CPU - Are the bare minimum CPUs the Wolfdale Xeons? Will any desktop CPUs be compatable? Does the machine need two physical CPUs to boot?
You should be able to boot without a graphics card, but that will be an easy part to find.  The Wikipedia article is quite good about processor families so you have several options there. The apple power supplies are top notch, but you might find an equivalent. 

Have you considered buying a scrap Mac Pro for it's power supply? I would be hesitant to spend money if I were not sure of the provenance of the stripped Mac Pro you have. (If the Mac worked, why strip the CPU, GPU and power supply? )

Good luck with your frankentosh!