|You cannot transplant an XP operating system harddrive out of one system ( Particularly a name-brand OEM product) into a different hardware environment and expect it to boot. XP ties itself to the hardware it was installed on.|
If you have a full XP Installation CD you may be able to perform a repair install to correct your problem and allow you to keep the original drive and all it's installed progs intact.
My personal recommendation would be to take the old drive out. Put a new clean drive in and do a fresh installation of an operating system. Then after you get it running, put the old drive in as a slave and transfer any files you want. You will have to reinstall any programs as they will probably not run from the slave drive.
Goin' Fishin' (Some day)