Do you have Internet Explorer?
If you do then try clicking on the second button that's up by the close window button. I'm not sure what the button is called, but when you hover over it, it says Restore down.
I've done that before on my computer, I had hit the F11 button on my keyboard and it got rid of the address bar. If you hit that button the address bar shows up so try that too!
Hope that helps.