Dilbert,
The same thing happened to me. I downloaded IE 7 but i could remove it
Control panel>>Add or remove programs
Click show updates
Remove IE 7 beta
You will be prompted if you want to roll back.
I know its faaaar to late but this is useful for things like media player 10 (AKA Sucky McSuck Player) and other beta things.
Incidentally, after rolling back to 9 a few months ago I did a system restore yesterday and its gone back to 10. This time I really can't roll back!