Let say you want to change native os application, desktop application was writeln using QT framework.

At the time of writing this document desktop app is compatible with 4.8 QT 5.x QT version. For compiling on windows I use.

http://qt-project.org/downloads (Qt 5.2.1 for Windows 32-bit (MinGW 4.8, OpenGL, 634 MB))

Desktop client source can be found at

https://github.com/LiveHelperChat/desktop

With install comes Qt Creator application which should be used to compile application. So just run it and open lhc.pro file