I guess if they were yours, it wouldn't be a problem. I've installed Ultimate on my desktop (already had & still have Pro), put a fresh install of XP ProSP3, Vista SP2 & Windows 7 Pro on my laptop. And installed Office 2010 Professional Plus on my desktop, too. Honestly, I doubt anything would happen, but there's those who gets carried away. Like doing paid upgrades for others. That is against the rules. At least now I know how some sellers on eBay gets their keys. A lot of the time, a seller has 10 keys of each Windows 7 version, followed by 10 keys for each Vista version, followed by 10 keys for each version of XP. I had often wondered how these sellers all came up with the magical number of 10, followed by a statement that the keys were issued by Microsoft. Now I know how it was done. That's clearly abuse of the program, and that's what I'm talking about. If a close family member needed an upgrade, yes, I could see that. But to upgrade all of your friends computers, no, that would be abuse. And there's certain products, like Office 2010, you can't even burn a disc of, you download it, and install and activate it on the computer you downloaded it to. So if you have four computers, yes, but if not, tread carefully. The keys that are issued to you are kept up with by TechNet. I've already been asked three times for discs & keys, the answer is no, before the rest of the words are out of their mouth. I had to buy mine, everyone else can buy their own software. I've printed several copies of the deal and gave some out, even posted it on the library board (after inking out all of the forum information with a magic marker).