Can't open new File Explorer windows by right click on Windows 10

I had the same problem and was able to pinpoint the culprit by using the excellent (and free) Shell Extensions Manager 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).

1. Save your work.
2. Launch shexview.exe
3. Run taskmgr.exe (Task Manager) and kill all explorer processes (in the "Details" tab).
4. Disable all extensions in Shell Extensions Manager (select them and choose "Disable selected items").
5. Run explorer.exe from Task Manager > File > Run new task.
6. Check if the behavior is fixed. 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.
7. 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.
8. 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.

I had the same problem, on two computers, which I've been annoyed by for months. The problem instantly disappeared on both when I uninstalled WinCDEmu just now.

Maybe you have that or a similar program installed?

Edit to clarify: WinCDEmu loads up disc images like ISOs as virtual disc drives. Similar programs might include Daemon Tools or PowerISO.

I found this solution here