Like Ted says, don't touch the Nvidia (or AMD/Intel for that matter) controls. They only adjust the color in software (change the bits that are sent to the display, not the display itself), which DisplayCal resets because it has to access the display out untouched. You can only adjust the backlight, so at least do that to ensure that you correct only for color and not luminance.
The only laptops I am aware off that offer hardware access to the displays are Apple macbooks (even the earliest macbooks), but probably only in OSX. (It would be cool if the DisplayCal authour could figure out how to access this in Windows when running Bootcamp)