Replace it with a new Windows7 machine. Or even better, a Mac. Problem solved. ;\)

Seriously though, +1 to all of the suggestions you've already received.

RAM is a good idea. I've known many "slow" XP machines that came with only 256 or 512MB of RAM. If this is the case with your friend's PC, upgrade that memory if the motherboard supports it. 1GB is good, 2GB is better. Makes a world of difference with XP, and the cost and time involved to upgrade RAM is usually trivial.

M80v2 | VP150v2 | QS8v2
SVS Pci+ 20-39
Emotiva UMC-1 & LPA-1
M22ti + T-Amp, in the Office