QT is a toolkit for creating user interfaces, so you use QT to compliment a programming language to easily make things like text boxes and buttons, for example. I would suggest starting with python (which you can code for and run right on your NIT device), and then, once you're comfortable with the language by itself (just using it in the command line), tie in QT to start making consumer accessible applications.

Quick note on python vs C/C++ - python is much easier to code for at the expense of system resources. When I was in your shoes, I would be thinking that if that is the case, clearly, C/C++ is the way to go. Stick with python when you're starting out, you will be much happier.

With python, you can easily write your code on your current windows operating system, but eventually you're going to want to switch to a linux distribution. An easy way to use a linux distro for programming would be to virtualize the maemo sdk image (essentially Ubuntu with a bunch of tools added on for programming maemo), giving you access to all of the tools from within your windows OS. - http://maemovmware.garage.maemo.org/2nd_edition/