MacMini Dock/Menu Have Disappeared

This is not a new computer, but it is new to us.
Model Number: A1347 (From bottom of computer)
Invoice description: Mac Mini 2.4GHz Intel Core 2 Duo, 2GB, 320GB, SuperDrive, Airport, HDMI, GeForce 320M
Originally purchased 2 years ago.

I allowed someone else to use my account on our Mac Mini and now my menu bar has disappeared, as has the dock. As well, the zoom function does not work, in or out. The only thing I can pull up on screen is a collection of three apps, consisting of the calculator, calendar and weather, using one of the top buttons on the keyboard which shows a circle that looks like a dial. The view seems to be zoomed way in, but when I move the pointer to the edge of screen, in any direction, the desktop does not re-center itself as it does when logged on to our other accounts on the same computer, so I cannot access the menu bar, or the dock. I would appreciate any suggestions as my account is useless at this point.

He has likely lowered the resolution and if you're connected to a TV possibly turned on/off overscan.

Try booting into Safemode and see if that will reset your resolution for you.

Press the power button
Immediately press and hold down the 'shift' key.
You can release it after you see the Apple logo on the screen.
Let if finish booting into safemode - it will take longer than you're use to.
Then try re-booting.

Thank you bobtomay. You have restored both digital and family harmony.

Let that be a lesson to you -- NEVER EVER let someone else use YOUR account. This is exactly why OS X allows for guest accounts.