While installation you have to assemble your Qt toolchain. Take the most recent version of Qt compiled with MinGW.
Although the installer provides its own bundled MinGW compiler Toolchain its recommend installing it separately because Qt is missing MSYS which is needed to compile and install OpenCV and OpenAL. Thus you can - if needed - deselect the tab "Tools".
The following steps assume that Qt is installed at "C:\Qt". If you decided to choose another location, replace corresponding parts.
Clone the repository (https://github.com/tux3/qTox.git) with your preferred Git client. [SmartGit](http://www.syntevo.com/smartgit/) is very nice for this task.
The following steps assume that you cloned the repository at "C:\qTox". If you decided to choose another location, replace corresponding parts.
Afterwards download the source archive of OpenCV from [http://opencv.org](http://opencv.org/downloads.html). It's recommended to download the Linux/Mac package because the Windows package is bloated with useless binaries. The Linux/Mac package only contains the sources and works perfectly on Windows.
Extract the content of the source archive to "C:\qTox\libs". Furthermore, create a new directory named "opencv-build" in "C:\qTox\libs".
Now you should have the two directories "opencv-x.y.z" where x.y.z is the version of OpenCV and "opencv-build" inside your "C:\qTox\libs" directory.
Run CMake (cmake-gui) and set up the input boxes "Where is the source code:" and "Where to build the binaries" with "C:\qTox\libs\opencv-x.y.z" and "C:\qTox\libs\opencv-build". Press configure and choose "MSYS Makefiles" in the drop down menu and "Use default native compilers". Press "Finish" to start configuration. TODO
The following steps assumes that you cloned the repository at "/home/user/qTox". If you decided to choose another location, replace corresponding parts.
Now you can either follow the instructions at https://github.com/irungentoo/toxcore/blob/master/INSTALL.md#unix or use the "bootstrap.sh" script located at "/home/user/qTox".