Microsoft has released a bulletin, but not a fix, for an issue that affects Aero users that switch from Aero to Basic and back. If you do this multiple times, it may get “stuck” and not switch anymore. So far, there is no fix, by Microsoft acknowledges the problem and are working on correcting it. I’ve seen a few people have this problem in the Microsoft Answers forums, nice to know that it is a known problem, even without a fix.
Consider the scenario where you decide to