So I'm building another computer for XP games and i have a few questions.

1) Is Xp Pro 32 the correct OS? I do have Xp Pro 64.
2) Motherboard is NVidia nForce500 Series Chipset ala NF 570 SLI. Will ATI video cards have ANY issues on the KN9-SLI?
3) I love my Abit motherboards and i certainly have a few. However am i just wasting my time as I do have Dell Socket 775's with Q6700 CPU's. Namely Optiplex 745, 755 & 780 MiniTowers. The Dell 780 Runs DDR3. I also have a Optiplex 7010 w/i5CPU & DDR 3. I know the all the drivers are out there for the Abit boards I have. I'm not so sure yet if the Dell's have XP drivers or not.
4) Do i need two different XP computers? Meaning one for the older games and one for the newer?
5) These are the video cards I have below ATM. Should i look for better?

ATI Radeon AIW 9600 XT 128MB
EVGA NVIDIA e-GeForce 6200LE 256 MB DDR
EVGA e-GeForce 8800 GTS 320MB (I have two of these)

Thanks