I purchased a 7" lilliput touchscreen brand new from a seller. When it arrived the monitor portion appears to work for VGA. After downloading the newest drivers, installing them, and plugging in the USB cable, Windows XP says that it detects the touchscreen and installs the drivers successfully. When I touch the screen nothing happens.

It's as if nothing is connected. Could I be doing something wrong or is the unit just defective? If so, does anyone know how to exercise the warranty? Please help! I am pulling my hair out here. Has anyone run into this situation?
Thanks,
Mark