Tab Key Behavior

Why will the tab key, inexplicably, start minimizing the current window and open another program on the task bar when pressed?

This has happened to me many times and was always corrected by rebooting. A friend is asking me “why” this happens and I don’t have an answer.

I have searched Microsoft’s technet site but have not come up with an answer.

Let’s assume that the current keyboard has been cleaned, and that using another keyboard has also been tried, but the problem persists.

What would cause this??

Sharon