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I haven't used the software Screen Spanning Doctor personally, but I from the discussions on this forum and others, the software works very well. If it were to mess up your screen configuration, i believe all you have to do is reset the PRAM or NVRAM. I don't know if the software works with Leopard though.

http://www.rutemoeller.com/mp/ibook/ibook_e.html
 
I have used the Screen Spanning Doctor for years--through both Tiger and Leopard--on my ibook G4. I couldn't function without it. Never had any issues.
 
Screen Spanning Doctor PROBLEMS

Just installed SSD on my 12" 1.33 GHz ibook G4. Super cool at first - saw the unlocked resolutions and changed to 1920x1080. Then decided it would be interesting to see the 90* rotation view. BIG mistake. did not work- screen looked weird then went blank. had to shut down and restart without external monitor connected in order to see anything but a blank, grey, blue, or weird screen. now I cannot even get the regular mirror setting to work- no external monitor viewing at all. 1) won't recognize external display unless I restart with it already connected. 2) even then, only shows blue screen (color of my desktop) but nothing else anywhere to be found. 3) with Screen Spanning Doctor enabled, still get weird looking screen - external display still appears rotated 90 degrees based on mouse pointer movements, but cannot see anything except gray hash. Tried disabling ScreenSpanningDoctor, deleting it from trash, resetting PRAM and NVRAM (unless they did not reset for some reason though I followed apple's instructions), and repaired disk permissions. Still same situation. Would be thrilled to get settings back as if I never installed SSD. Please help. Thank you.
 
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