If you search the web for Alt Tab Bug you will find many reports of an annoying problem with the behavior of the Windows 7 Alt+Tab feature. Alt+Tab is used to cycle through the set of running programs in order to change to a different one – you hold down Alt and repeatedly press Tab to cycle through the programs. Through the magic of Aero-Peek you can see a grid of icons and miniature windows on top, then below that the currently selected program, and below that the desktop. The important thing is that the grid of programs should look like this and should always be on top:
On some machines, for reasons that are poorly understood, the grid of icons and miniature windows ends up behind the currently selected program. That often means it is invisible, which makes Alt+Tab almost impossible to use. The grid of programs ends up being partially or completely obscured, as shown here:
I lived with this behavior for far too long. For me it is the most annoying bug in Windows 7, and I finally decided to investigate. It took me about five minutes to find the problem, or at least the problem on my machine.
Update: more recently I investigated more deeply and I found a solution. You can get the full explanation and a program which will fix the bug here.
I started by shutting down all visible programs (Outlook, Internet Explorer, Visual Studio, etc.) and shutting down many programs in the notification area. As I did this I repeatedly checked to see if the bug was still present. It was.
Then, with just Task Manager running I started going through its list of programs, killing (with End Process) anything that looked non-critical, and checking after each one to see if Alt+Tab was working.
That was the culprit.
ipoint.exe is the Microsoft Intellipoint mouse driver, and it is the culprit. I don’t know what this program is doing, and I don’t know whether the bug is in Windows 7 or in the Intellipoint mouse driver, but it is safe to say that the bug is in Microsoft software.
When I kill ipoint.exe it always restore the correct Alt+Tab behavior. When I run ipoint.exe it takes a minute or so before Alt+Tab starts misbehaving, but it always eventually misbehaves. I suspect that ipoint.exe exists in order to implement fancy mouse functionality that I don’t actually want (I think it has an option to remap the middle-mouse button, which is a bad idea) so I haven’t noticed any ill effects from having it not running.
I used autoruns to stop ipoint.exe from automatically running and the problem is now fixed on my machine. I suspect that this fix will work for many other people, and maybe the Windows or Intellipoint teams will fix the root cause some day.
Many reports on the web say that sidebar.exe (used for desktop gadgets) can also cause this problem. I don’t use desktop gadgets so I don’t normally have sidebar.exe running, but a few minutes after I added a clock gadget I found that the bug had returned, and killing sidebar.exe corrected the problem.
Since this bug appears to be caused by particular programs it is easy to investigate by shutting down programs until the bug goes away. If you find other programs that trigger this bug then please list them in the comments.
For now, if you use Alt+Tab and are hitting this bug, make sure that ipoint.exe and sidebar.exe are not running.
Happy task switching!
Update: after finding the problem and posting this entry I found that this thread had reported that ipoint.exe and sidebar.exe were the main causes.