Thank you that windows 7 types really helped. So if someone else have this problem: Just go to regedit andin HKEY_CLASSES_ROOT\Directory delete folders with "cmd" name
or just call your friend...

I already tried this and it didnt work :-/

Hi,
I have a problem on windows 10... sudenly there was a change to the default program that opens folders from explorer.exe to cmd. So if I doubleclick a folder it says there is no program assigned...