64 bit will run 32 bit programs just fine. The only problem you may have is getting 64 bit drivers for everything like printers, web cams, scanners and such. Most motherboard makers, sound cards, and video cards have 64 bit drivers out.
I have 64 bit but dont use it that much. Dont have any 64 bit programs to use right now.
I would dual boot 64 and 32 bit xp right now if you already have 32 bit xp. That way if you run into driver problems you can still use it.