My macbook suddenly thinks its display is 800x600 I have not found anyone else online who had this problem, which is troubling.

Here is all I know:
I closed my macbook (running Leopard, a few years old).
I opened my macbook.
The display had changed completely.

What I mean by that is that the resolution severely decreased, and all of the icons on my screen grew significantly in size, even though they all fit on the screen. I am certainly not in "zoom mode" (ctrl+scroll). I checked "About This Mac" and under resolution, I found that it says, "800x600." What? My resolution is much above that. I have no idea what prompted this. I restarted the computer, but it did not help. This is very worrying.

Does anybody know what happened, or how to fix it?
Thanks
Simple solution. Head into system preferences and click on the display icon on the second row. Click on the display bar at the top (on the left of colour) and scroll through your different display options (I recommend 1280 X 800 but you can have whatever you want. Double click on the display option you want and there you go!