ok so some questions to lead in the right direction:
What is the make/model# of the Touchscreen
What is make/model of TV
What graphics card are you using (you said Nvidia, but the model is important)
Are the Touchscreen monitor and TV hooked up to the ports for the graphics card? or the on-Board ports?
What version of windows are you running? (Home Premium/Pro/Ultimate)
Is your version of windows 64X or 32X?
Can you look in the Device manager and tell me if there are any devices with problems (yellow problem triangles).
Programs to use to find info:
CPU/Motherbord info: http://www.cpuid.com/cpuz.php
Graphics Card info: GPU-Z Video card GPU Information Utility
So here are the possibilities I can think of:
Driver issue: Windows 7 is supposed to have native support for touchscreens, but it sounds like it is treating it not as a screen, but a pointer device.
Graphics Card: It might be that your video card is only using one external monitor at a time because you cant use both ports at the same time. You might need to put one of them on your on-board (usually VGA) port.
or: there might be another issue as to your Motherboard. If this is the case, you would need to check online with the manufacturer of the motherboard to see if there is a BIOS update to fix the problem you are having.