My son is into computers and has 5 computers in his room (3 desktops and 2 laptops). Unfortunately, he has a non-legal version of XP on all his computers. I told him that this needs to be corrected and I would assist. My question is: What is Microsofts policy on XP for putting it on more than one machine? He mainly uses only 2 machines (1 desktop and 1 laptop). If I purchase one version of XP or Vista, how many machines can that be put on? What is microsofts policy on their license?