Microsoft will allow you to use a License purchased for the current version of Windows to be used to run older versions, as long as the newer version is removed from your machine. You can't use an older license for a newer version, but you can go backwards. So if you have a friend with Vista, you can use his disk to load the OS, but hold on to your 7 license to make it legal.
We are all kind of frustated with the dumming down of Windows that occurred in the XP to Vista to Win 7 process. A lot of the user functionality and control has been removed and replaced with automated processs to make it more similar to a Mac. Unfortunately Microsoft does not realize that most Mac users are nearly computer illerterate, and seldom use more than one or two programs. And we all are driven crazy by the random rearrangement of menu items and UI layout just to make it look different from XP. If it looked too similar to XP people would think that they are not getting their money's worth. So they felt obligated to scramble the menus to make it look like they did a lot of work on the XP kernel. But a new coat of paint is still just a new coat of paint.
But, that said, Win 7 is far better than Vista. If you dont like 7 go back to XP. Other than looking prettier, 7 does not offer any real functionality that XP didn't already have. And, until the first 7 service pack comes out, Xp is still going to be more stable. Don't cut off your nose to spite your face by going back to Vista.