I would really like some new version of Windows, regardless of the number, to really rethink the install/uninstall process. Really sandbox new software in and when you uninstall it, it really absolutely removes everything, instead of leaving garbage all over the system.

And also to improve the install process, let's please move beyond the install wizard. The user shouldn't have to click "next" 5 screens in a row where there are no options of any kind. Something more OS X-like would be nice.