this depends on the application. If it is written in ANSI C (no C++) and it does not use any Visual C++ User Interface elements, you should be fine compiling the source-code in LabWindows/CVI without any problems (maybe some paths would have to be adjusted).
LabWindows/CVI is an ANSI C compiler, so if you are using any C++ specific elements (classes, inheritance etc.) this will not work.
LabWindows/CVI uses its own system to implement the user interface, so if your program uses any user interface compnents of Microsoft Visual C++, you would have to redesign these in LabWindows/CVI.