How do I fix my desktop display back to default?

I accidentally pressed some sort of shortcut to change the desktop display and now I can't fix it. I have windows XP (2000?)

The screen is expanded to the maximum and the top internet toolbar now disappears until I move the curser to the top of the screen. Also the bottom toolbar only appears when I press the key with showing the windows icon.

How do I return the desktop display to default so that I can always see both top and bottom toolbars?

Thanks for your help

 

Probably F11.


EDIT. Sorry, I've noticed that you have just joined the forum and could be a newbie.

My "Probably F11" means press the F11 key to toggle full screen on and off.