Go to System Preferences > Universal Access and make sure that you do not have Zoom function turned on.
It is relatively easy to turn it on and I guess you may have done this accidentally.
P
Something strange happened as I was working on my iMac G5, running OSX 10.4.11. The desktop zoomed in and every time I move the mouse, the entire desktop moves as the mouse moves. It seemed to happen after I accidentally pressed the "control" key and another key (I am not sure which), but I can't reconstruct what happened or undo it. I tried System Preferences / Displays and changed the resolution, but it doesn't change. When I reboot, the start-up routine proceeds, the desktop appears normal for a second and immediately reverts to this bizarre desktop view. Any ideas?

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