Display Problem

Not sure what is going on but all of a sudden my 20" iMac's display has become screwed up.
It looks like it is set to a much higher resolution than it can cope with as only part of the desktop is shown, move the mouse and the desktop moves around...
It also looks like it is set to thousands and not millions.
I have tried resetting it to 1680x1050 millions but it doesn't change.
Please help because i feer a re-install is required.
Thanks

You've just zoomed in.

Hold down control and use the mouse wheel to zoom out.

No the Whole desktop was affected not just a window.
I ended up trying archive and install - didn't fix it.
Finally I jus deleted everything and did a fresh install - that fixed it.

Very Weird - Would love to know.....

Very Weird - Would love to know.....

Click to expand...

Well the poster above you answered that question....
Zooming with ctrl+mouse scroller does indeed zoom the whole desktop and not only windows.
And you navigate with the mouse in order to move around on the huge desktop you suddenly got.