...the "Languages" tab, press the "Details" button; in the "Text Services and Input Languages" dialog[|ue] that appears, juggle the "Language" setting in the upper combo-box and the keyboard selection in the lower tree/list-box.
I *think* that if you have more than one keyboard (or was it more than one language?) installed, the "Language Bar" and/or "Key Settings" buttons down just above the lower edge become enabled; IIRC, the "Language Bar" is what you want: A quick-switchy-thingy for these settings that you can leave visible on your "Task Bar".
HTH!
Oh, and BTW... Aren't you glad we've got a nice simple GUI to do this in, so we don't have to use a horridly complex command line?