I've taken the course for Windows 7 and as I'm informed, for the home users best buy would be "Home Premium" and for business users "Professional" version. With Home Premium you'll miss the following features from Professional: - Windows XP mode (do you need it? If you do, then you don't have a choice, take Professional version) - Domain Join - Automatic Backup Ultimate has all of that + - Bitlocker (useless for Home PC's, if you ask me, very useful for laptops) - Languages support (35 languages) so far. As my company has SA agreement, I'll have access to all version, but for the home use I won't need anything more than Home Premium. Many people will choose Ultimate so he/she can boast with it and say "I have it all", but I'll ask then, are you using features from the "Ultimate" version?