Is there anything on /media/mark?
If not, you might want to do this:
Code:
sudo chown -R mark:mark /media/mark
If yes:
Code:
sudo chown -R mark:mark "/media/mark/Back Up"
That is assuming that your group is mark as well as your user. You can find out with
PS: please use CODE tags for code, output and such (see my signature) - not quote tags.