Screen moves around with moving the mouse, 'System Preferences' does not open!!

I NEED HELP!

I am using Mac OS X 10.5.8

Screen moves around with moving the mouse, I have checked here that turning off Zoom from the Universal Access and Keyboard & Mouse panes of System Preferences would sort out the problem BUT my 'System Preferences' does not work, when I try to open it: nothing comes up. Please someone may advise if there is any keyboard commands to sort the screen moving issue.

(I know I need an upgrade, but there is massive data, family pics, movies to be backed-up before the upgrade, and I don't really know how to)

Thanks