I'm guessing you found the CPU on pricewatch, as all the listings say that. Anyways don't worry about it, it will work with your copy of Windows XP just fine. I'm actually using a 64-bit system right now, with XP. It just means that the processor is compaitable with the 64-bit version of Windows, but is also compatiable with 32-bit versions as well.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>