SCCM 2007 - Troubleshooting - "\WINDOWS\system32\CCM\VAppRegHandler.dll failed to register" during client installation.
Had several SCCM client installations fail with the error in the Application Log:
\WINDOWS\system32\CCM\VAppRegHandler.dll failed to register.
The solution for me was in this link:
http://social.technet.microsoft.com/Forums/en-US/configmgrgeneral/thread/252a063f-f380-4289-bbd3-2f55a77b6fa9
and in a nutshell, perform the following:
ccmsetup /uninstall
regsvr32 atl.dll
This solved the issue for me and I was able to install the client afterwards.