The window preview as you hover over the tasks in the task bar is addictive. Being able to see thumbnails of each application window makes it easier to pick which window to bring forward (another bonus for multi-taskers).
You seem like you know what you are talking about. Can you tell me how to disable this in Windows 7? I have somehow removed the thumbnail of the running application window, but a tooltip still appears even if mouse cursor reaches the toolbar accidentally, refusing to go away for a while, blocking my screen.