I had the same problem, on two computers, which I've been annoyed by for months.
When the culprit is found, just leave it disabled and the issue should be solved! You can report the bug to the developer of the responsible app so that they can fix it.Enable some extensions starting with those you think are unlikely to cause an issue (in my case it was a 'Context menu' extension from Boxifier), and repeat steps 3-6 until you have found the culprit.If it is, then continue, otherwise, reenable all extensions previously disabled and continue looking for an alternative solution as this one will not help you. Run explorer.exe from Task Manager > File > Run new task.Disable all extensions in Shell Extensions Manager (select them and choose 'Disable selected items').Run taskmgr.exe (Task Manager) and kill all explorer processes (in the 'Details' tab).
Here are the steps which worked for me, and not tied to a specific program like WinCDEmu (although it should also fix it). I tried using autoruns from Sysinternals but the latest version as of this writing was very buggy, so I would strongly recommend against using it. I had the same problem and was able to pinpoint the culprit by using the excellent (and free) Shell Extensions Manager by NirSoft.
