As soon as you turn the PC on, keep hitting the `delete'key until the BIOS page appears.Allowing for different BIOS designs you will probably find the boot sequence under `Advanced Bios Settings' where it should be in the order A, C, CDRom. Following the instructions at the bottom of the BIOS page, change the sequence to A, CDRom, C.insert your XP Recovery disk in the drive and exit the BIOS saving the changes, usually F10. Your PC should then boot up from the CDRom and recover your Windows installation.
If successful, remember to re-enter the Bios and change the boot sequence back.