It’s basically the same as using VirtualBox, except XP Mode doesn’t require an extra XP license. Of course, if this is the only feature in Ultimate you want, you can find freeware or cheap backup applications for much cheaper than the upgrade fee. Here’s the real differences that might matter to you, the home user:
Microsoft has a comparison page where you can see the very detailed list of features that differentiate each version of Windows from another, but it’s a lot of information to take in. Differences Between Home Premium and Ultimate
