Performance should not be an issue on the FE, so find one you like.
As for OS, with that processor, you probably wont need the boost that 64bit XP gives you, as it wont be enough to bridge the gap to newer games.
If you want to play some games that you think might be questionable on your hardware, check it out on 32bit XP, if you are within 15% of how fast it needs to be, then it might be worth trying 64bit XP.
Else with that setup, I would probably just settle on 32bit XP and console emulators to fill in any gaming gaps.