Try checking the boot device order in the bios. (Hit delete key on boot)
Set cdrom as first boot then hd0 as 2nd
Just connect the 1 harddrive that you want to install xp on.
Make sure cdrom isn't sluggish---try a different one.
Make sure cd isn't damaged or dirty.
I have had a few xp cd's i burned do the ntldr missing and it has to do with the cd being able to boot.
Hirens boot cd is a fabulous tool--everyone should have one for the day when their xp stops booting or the mbr gets messed up and no matter what you do it'll break again in a short time. Insert cd in 2nd drive and boot.