I dont think his computer can even properly run Windows 95. Man, you should start a charity for your friend. xP.
Trying to install XP would either
1. Destroy his computer,because it requires atleast 250mb of HD space to install, fast proccessing speed, 128 ram, etc.
2. Just deny the computer access to install
3. Show a pop up that says "Sorry, Windows Xp is only for cool people"