I don't believe Labview 5 is officially support under XP, but I have heard that it works.
As for 2000, it also appears to work, but you may want to check out this website.
http://labview.brianrenken.com/INI/obsolete.shtm
I don't know about Millenium.
-Matt Bradley
************ kudos always appreciated, but only when deserved **************************