IF YOU HAVE TRIED VirtualDesktopGridSwitcher AND IT FAILED TO RUN YOU PROBABLY NEED TO "UNBLOCK" THE ZIP FILE IN FILE PROPERTIES BEFORE EXTRACTING
Also, if another program is already using a "hotkey" key combination used to switch desktops you will be warned that it could not be assigned. You will either need to change the key combinations in settings (see User Guide) or find out what is using it already and stop it from doing so. Often your graphics software has some of these keys assigned - try right clicking on the desktop and look for Graphics Options -> Hot Keys or Graphics Properties -> Options.
See the Installation Guide in the Wiki section for more information