If it won't boot from CD rom, make a bootable floppy, like a Windows 98 boot disk.
You can download an exceptional one here.
Have the XP CD inserted in your CD/DVD ROM drive, and boot to the floppy.
At the command prompt, type:
E:\i386\winnt.exe
(where E: is the letter of your CD drive)

Or you can try one of the XP install boot disks from that ^ site. I've never used one though...