IsThreadDesktopComposited prevents program startup

Problem: a NetScanTools Pro v11.10 user emailed with a strange problem. He could not get NetScanTools Pro to start on Windows XP sp3, instead he would get this message: "Entry Point Not Found. The procedure entry point IsThreadDesktopComposited could not be located in the dynamic link library USER32.DLL."

The first thing I did was use Dependency Walker to see if our program called that entry point in user32.dll. It did not. So I searched online and found the answer.

Apparently some misguided installers are putting a Vista file called dwmapi.dll into the Windows XP Windows\System32 directory. Some programs like NetScanTools Pro v11 are affected by this and give the IsThreadDesktopComposited error. Some people have noticed this happening after a Windows Live Messenger or Mail upgrade but I have not independently confirmed this.

Solution:
1. locate dwmapi.dll in the windows\system32 directory
2. rename or remove it
3. reboot to be sure it's unloaded from memory

This application has failed to start...

Have you ever seen that message? You know, the one that says "This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem." (that's what it says on Windows XP - Vista and 7 have a more informative message). The message should read: Windows is missing important files that should have been downloaded through automatic updates -- oops!

What this usually means is that the Visual C++ redistributable fileset is wrong, either too old or missing one or more pieces. These are the Side by Side DLLs we are talking about. They reside in the C:\Windows\WinSxS directory and the have rediculously long names. Those names include the version of MFC, runtime, etc of the DLL. This problem happens most often when the compiler has a new revision, like last July 2009's revision of Visual C++ 2005.

Fortunately the fix is pretty simple. You have to find the Visual C++ redistributable installer that is missing and run it. It's installer takes care of the rest and it is a pretty fast fix. But you have to know which one to use. Our software installers look for signs that the SxS DLLs are there, then run the redist installer if they are not found. You may have to contact the software vendor to find out which one to use. Kind of a pain.

I'm posting this because one of our customers had this happen today. Fortunately he emailed and I was able to give him the link to the proper redistributable installer. It fixed his problem.