What is it? a 486? Here is the link to a new Linux Distro made to look like XP. The hardware requierements are quite low (Pentium 300MHz / 128MB RAM / 3GB disk) thus it is likely to run well on that old PC that came with M$ XP. http://www.q4os.org/
Ive been trying out q4os which is designed for lower hardware requirements. So far it looks a well thought out distro with some nice features for beginners. The homepage has more info.