Quote from Passive Pete:
Great point. What would you recommend? 64 Bit? I really don't know what to get.
If you want to be safe... assured that all of your apps will run and all of your peripherals will work, you get WinXP Pro. It will be good until at least 2014.
Most apps are not in 64-bit yet. So even if you have a 64-bit OS, most programs will run in "32-bit emulation"... which is OK.
There is some risk that some things will not work properly with a 64-bit OS.