Being a software developer myself, I avoid bootleg software and I like to stay in compliance with the license terms of software I buy. (Yes, I know that many people don't care about such things.) I own two copies of MS Office: MS Office 2008 for Mac, Home & Student Edition. It allow three installations, plus one more on a laptop used by the primary user. It is not to be used for commercial work. MS Office 2008 for Mac, Special Media edition, just purchased. It allows one installation, plus one more on a laptop used by the primary user, and it can be used for commercial work. (Actually, I'm assuming it shares a license with MS Office 2008 for Mac Professional since the Media Edition came with no license statement in the box or on the disc.) Here's the status of my 4 Macs: Desktop Mac 1: installed copy of Office H&S Edition, used for personal work Desktop Mac 2: installed copy of Office H&S Edition, used for personal work Desktop Mac 3: installed copy of Office H&S Edition, used for personal work Laptop Mac 4: no installed copy of Office yet The issue is that I want to start doing commercial work on Mac 3 and on the laptop, and that's why I bought the copy of Office Media Edition. Perhaps I could simply consider my purchase of Media Edition to have authorized my commercial use on Mac 3 and Mac 4, but to do things properly I should change the license on Mac 3 from the H&S Edition to the Media Edition. Is there a way to re-register an installed copy with another key, or do I need to run the H&S Edition uninstaller and then the Media Edition installer on Mac 3? In either case, I'll run the Media Edition installer on Mac 4. Is there any "gotcha" I need to watch out for when changing versions of Office this way?