I had the same problem and was able to pinpoint the culprit by using the excellent (and free) by NirSoft. 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. Here are the steps which worked for me, and not tied to a specific program like WinCDEmu (although it should also fix it).
Save your work. Launch shexview.exe. Run taskmgr.exe (Task Manager) and kill all explorer processes (in the 'Details' tab).
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Disable all extensions in Shell Extensions Manager (select them and choose 'Disable selected items'). Run explorer.exe from Task Manager File Run new task. Check if the behavior is fixed.
Apr 08, 2018 Please Help. I Suddenly can't Open Any Folders, or This PC. In a nutshell, I can't open 'This PC' or any other folder that is on my desktop. File Explorer won't function either. Whether I double-click, or do a right-click and choose 'Run', all that happens is the little hourglass comes on for 1/10th of a second. Still can't open any.
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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. 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. 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.