XP doesn't travel well. Take a google of these words to see what you are looking -> XP CHANGE MOTHERBOARD AND SAVE OPERATING SYSTEM.
Can I do this to make the newer Vista computer a dual boot? I have an old hard drive with XP on it. There are also quite a few programs that I want to keep and can't be loaded on Vista. I obviously must make sure the new computer has an IDE connection for the old hard drive. The thing I'm most doubtful about though is whether or not Windows Boot Manager will detect the additional hard drive with XP on it and decide to make it a dual boot.? What do you think? Is there anything else I should be checking?