After reorganizing folders on my network shares, my Windows machine (VirtualBox) would refuse to start the Explorer or ‘My Computer’. The solution is to fix ‘User Shell Folders’ settings in the registry editor.
The above error message appeared whenever I attempted to open an Explorer window or ‘My Computer’ (which is also an Explorer window).
The fix is to make sure that there are no inaccessible paths in the
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
In my case, I had forgotten to enter the correct credentials when I mapped
X: to my network share. As soon as I fixed this, everything worked