On the one that isn't working properly, try and see if the video card driver for your model of card has been installed. you might find it is only using Default Video Adapter driver, you can find out by going to (in XP) - Display in Control Panel, goto Settings, Advanced, Adapter.
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On the one that isn't working properly, try and see if the video card driver for your model of card has been installed. you might find it is only using Default Video Adapter driver, you can find out by going to (in XP) - Display in Control Panel, goto Settings, Advanced, Adapter.