First go into the BIOS for your hard disk and make sure you have it set to boot from the CD/DVD first in the boot priority.
Then after you set it and save it, reboot and during the reboot watch the screen closely. It should prompt you (Press space or some other key to boot off CD/DVD). Hit the key and it should begin to boot on the Windows XP CD and begin the install.
answered Jan 26 '12 at 19:13