there is a hidden folder with the rc file in it
on my kde4 desktop it is located in
/home/UserName/.kde4/share/config
/home/UserName/.kde4/share/config/digikamrc
the folder settings are in that file
it might be easiest to just rename it and restart digikam
Code:
mv /home/UserName/.kde4/share/config/digikamrc /home/UserName/.kde4/share/config/digikamrc.backup