Do I need a 64-bit CPU to run Win XP? Or just to run 64-bit applications?
The second one is my guess.
Unless you have a 64 bit version of XP (XP 64) then you don't need a 64 bit processor for XP to work, just for any 64bit applications to work.
Having a 64bit like my AMD Athlon64 3700+ makes XP fly though
So there are 2 versions of XP...one each for 32 and 64 bit processors? Is the 32 bit version "forward compatible" if I upgrade later to an Athlon 64?
I am running WindowsXP HE (32bit) on my Athlon64 so yeah 32bit OS's are fine for a 64bit processor. A 64bit OS wil however not work on a 32bit processor.
Windows XP 64bit Edition is not worth the change from HE or Proffessional. Lot's of people have gotten it and after a week of use have gone back to their 32bit OS's. It's more buggy and problematic than normal XP. Also the 64bit edition is highly incompatible with older games (AoE2 for instance) and applications.
(OS = Operating System)
Lets clear this thing up
YOU NEED A 64-bit prossor such as amd 64 3xxx+ or an intel 6xx series or above, to run windows pro 64-bit
there are curtly 3 virsions of windows XP HOME XP PRO and XP PRO -64-bit
i woulnt get windows pro 64-bit yet because of the lack of driver support and it slows down some 32 bit apps