Delete these keys or values from the registry. This will reset many things like saved folder settings.
Type Regedit in Start - Run
Click Start - Turn Off Computer (or maybe Shutdown) - Ctrl + Alt + Shift + click Cancel (or Close) (your Desktop and Start Menu now disappear).
In Regedit navigate to each of these keys and delete them
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer and delete the value
Shellstate
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState and delete the value
Settings
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Streams
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\StreamsMRU (may not exist)
HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\BagMRU
HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Bags
HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\BagMRU
HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\Bags
[the above one is what reset deletes, 90% of the time it is sufficient but 10% of the time the BagMRU needs to be deleted too. If you know what cross linked files are the same thing is happening here - the BagMRU point to the wrong Bag or serveral BagMRU point to the same bag]
Then in Task Manager, File - Run type explorer. (Start menu and Desktop come back).