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.
The investigation
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.
ipoint.exe.
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.
Other causes
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.
Conclusion
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.
Random ASCII - tech blog of Bruce Dawson 
Strange… 2 days ago I first read about this problem here, today I encountered it. Closing the sidebar got rid of it, but I like the sidebar. Thanks for the post anyway!
It is pretty lame that Microsoft makes you choose between sidebar/ipoint and Aero Peek. If you like the sidebar then you might want to turn off Aero Peek. Unfortunately, if you turn off Aero Peek to fix the alt+tab bug it also turns off “Peek at desktop”.
Bottom line, of course, is that alt+tab should be fixed.
This is the second bug (AFAIK) that is solved by killing sidebar.exe! A few months ago, my calendar widget became completely orange. Removing and re-adding it to the sidebar did not work. Logging off and on again worked sometimes. Killing sidebar and restarting it not only solved the problem for the current session, but made the bug go away completely.
Now sidebar strikes again! I noticed the Alt+Tab problem and killing sidebar.exe solved the problem. I don’t know if I will have to disable it permanently or not. To be safe, I will keep only the calendar widget and remove the clock.
Well, keeping only the calendar was not enough. I don’t know what kind of weird interaction occurs with Alt+Tab, sidebar and video drivers, but it seems that it started to happen to me only when I switched to the integrated Intel video of my motherboard. When I reinstalled my GeForce graphics card, the problem went away (it’s OK so far, but who knows what will happen tomorrow).
i stil have the ALT-TAB broblem and i searched for the aplications that where cousing the problem named in this post. i could find them and the problem is stil there. its extreemly frustrating plz help me with the problem.
I can only suggest firing up task manager and killing processes one at a time until the problem goes away. Keep track of what processes you are killing so you will know which one is the problem.
The root cause is not known so potentially any program could be the culprit. My list cannot be complete or authoritative. Let us know what you find.
Complain loudly to Microsoft if possible. They should fix this.
thanks for the help but the problem suddendly just went away so im just gona keep it this way. i hope the people at Microsoft are fixing it. its annoying.
if noticed that my mcfee was trolling me same as i got the atltab problem this is what u wana do if u got both problems.
(step1)
http://us.mcafee.com/root/fix.html
folow the steps there (i recommend removing it going to log in pace redownloading it and reinstalling it)
(step2)
during installation it wil tell u it enconterd some problems. it wil scan ur pc and fix some problems.
when done with installation of mcafee white screen wil be gone and you can scan ur pc. it also fixes the alt-tabing problem.
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brucedawson, I’m with you … I wrote Cisco’s Transceiver Driver Library for the Nexus 7000. To be sure there were no bugs, I wrote a simulator which ran on Windows using Visual Studio (even though the switch used Linux). That way I could introduce every situation that has come up in the past and everything I could think of for the present. By the time the library got onto the switch, the only “bug” was due to someone giving me wrong specs.