Any processor with a mathco processor can run XP, I believe. Sure, anything with a mathco processor can run any OS but the speed...well, lets just say it won't be fast :P
I have ran a 300mhz celeron with 64mb ram on XP fine.
Btw, those that may have issues with it being "slow" should read what I am about to say. Windows XP once again didn't turn on UDMA by default. If you have a fast drive, you should always turn on UDMA, it makes such a big difference... performance wise
Well, thanks for reading!