I recently bought a touch screen off ebay. I hooked it up to my laptop and tested it to make sure it works. It does (only one dead pixel)! The next step was to hook it up to my desktop in a dual head configuration.
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This wasnt difficult to do by any means, but it was a little bit tricky finding the option to set the screen order in TwinView. I have two monitors (one LCD w/ DVI and the touch screen TFT with VGA). By default, the Nvidia driver sets any VGA connection to screen 0. With a bit of digging, I found the TwinViewXineramaInfoOrder option from Appendix D of the Nvidia Linux Driver Readme/Install Guide: