Right-Click on Desktop....

[Karibu]

Facts:
Laptop HP Pavilion g6-1b67ca running
Knoppix 6.7.1 from USB flash drive.
Boot with cheatcode "nomodeset" (for graphic card reasons).


Hello,
"Right-click on Desktop" is not opening the pull-down window after I accidentally check-marked
in "Desktop Preferences" under Advanced Tab the box "Show menus provided..." and closed the
open window afterwards (see Screenshot).
I was not able to get the "Right-click on Desktop" option back yet. What can I do?