If you are using a Thinkpad which doesn't have a "Windows" key, then some of the default key bindings will not work. So you have to edit the key binding configuration file to make them work. Just follow the following steps to do it.
1) Go to /home/YOURUSERNAME/.config
~/.config
If you see a directory
cp /etc/xdg/openbox/rc.xml ~/.config/openbox/