The only solution that work propperly and i have tested after many reboots is:
Open regedit.exe.
Go to the Section->
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\GameUX\
Delet the registry entries/Key:
S-1-5-21-1380981980-2726883197-928252028-1000 / May be different
leave only these Keys:
Games + Machine Settings DON'T DELET THESE KEYS!!!
Thats all. No reinstall. My Flight Sim has 29 GB and over 170.000 Files! :-) :-) :-)