Quote - http://www.syschat.com/dual-boot-vista-xp-vista-already-1946.html

Google is your freind.. ;)

I googled "adding xp dual boot to vista", and used the first hit.. ;)

How about the oposite?

Dual Boot Vista 64 and XP with WinXP Pro already installed

"That government is best which governs the least, because its people discipline themselves."
Thomas Jefferson