First, I wish to know if Xp is compatible with new 64 bit processors and if using XP will dramatically limit the advantage of upgrading to a new motherboard and cpu. I really don't want to get into a new operating system ie. Vista and I haven't heard much about Xp 64bit edition so I assume it was DOA. I also wish to know what is this deal about 4 Gig memory limit with XP and if it means must be less than 4 or can be exactly 4. I heard that from 3 to 4 gives no advantage. Thanks in advance.