you probably have a shortcut of desura somewhere on your desktop or in your startmenu, right?
right click on that, choose properties and in the target field you will see the path of your desura executable.
in that path ("D:\Program Files (x86)\Desura\desura.exe" for me, take away the desura.exe) you will find a directory named "Common" and in that one is the "Xenonauts" folder.