To answer the question...
If it's a one hard drive machine, pop the xp disk in and turn the pc on. The disk should automatically run. If it doesn't, reboot, and access the bios. Then change the boot order so that the cd drive is the first boot device. Then save changes and exit.
This time it will run, follow the instructions. If you have more than one hard drive installed & there is stuff you don't wish to lose, be sure to install xp on the correct drive. I stuffed that one once & lost ooh a thiusand albums or so...
