We are living in the 21st century and XP is dead now and needs upgrading for MANY reasons! I've been servicing XP since it came out.

I recommend Windows 7 over Windows 8 and it is still available to buy.

Regarding 64 vs 32bit. The fact that its only a memory issue, what is the big deal here? You can see from my computer spec listed below that mine is a Hi End PC yet I have no problems at all. So whats the big deal with 32bit BIAB?? Storm in a teacup comes to mind.