|When you boot to the windows xp disk it gives you an option to delete the partition. You delete them and then install xp.|
This assumes that xp supports the system. A newish system would have to have sp3 slip streamed in and usually some drivers added in to a new cd to use to install.
There is a chance that the original recovery data is on the hard drive or you might be able to purchase the media for a small fee from the company that made it. I would be suspicious however, the thing may be stolen.
Text, talk, drive...CRASH.
Hang up and drive @#$%^^