By accident I added left mouse click as a shortcut for toggling fullscreen for the active window. That won't allow me to get back into user preferences to rechange it. Is there any other way to change keyboard shortcuts?
This shouldn't affect anything if you're clicking directly on buttons but you can use CtrlAltU to bring up your user preferences or press Space and search for it there. Next go to the Input tab and look for a button next to Window marked Restore (Blender remembers what changes you make and offers a handy way to reset only that section without messing up any other keybindings you remapped). From there you can use to set it back to the default value of whatever config preset you are using.
If you have nothing to lose you can also bring up the space menu and type load factory settings then save that as your new startup settings.
There are several ways to restore the factory settings.
Open a command prompt, (press the windows key + R on windows, type "cmd" and press enter if you're using Windows) and navigate to the folder in which you installed blender by typing "cd .." to go to a parent directory, "cd [name]" to open a folder and "dir" to display the possible folders. Now type "blender.exe --factory-startup". Blender will open and you should be able to change and save the settings.
The blender wiki gives two other ways to restore the factory settings.
- Go to File Load Factory Settings and then save the preferences with CtrlU or via the User Preferences editor.
- Delete the startup.blend file from the following location on your computer: Linux: /home/$user/.blender/'Version Number'/config/startup.blend (you'll need to show hidden files). Windows 7 and Windows Vista: C:\Users\$user\AppData\Roaming\Blender Foundation\Blender\'Version Number'\config\startup.blend MacOS: ~/Library/Application Support/Blender/'Version Number'/config/startup.blend (you'll need to show hidden files, or press "command shift g" in a finder window, and input the path).