Multiple Monitors

Having trouble with connecting laptop to second monitor - all I can get is the background. Mirroring does nothing, nor does correcting the resolution.

Last time I hooked them up it worked seamlessly but not today.
I don't understand what's going on, so can somebody point me to a how-to or tutorial of some sort that gives me the technical details? Maybe if I knew more about it I could troubleshoot.

Nothing I've found online is making any sense juxtaposed with what I have in front of me. Really confusing.