@Chris-Kawa thank you for your response! I know that there is no 64bit VS, and you are right about the 64 bit builds, I just don't know how to do it :) I managed to get rid of the problem written above by removing qtmain.lib from the lib listing, and VS builds the app succesfully. I just downloaded the 64 bit Qt version and will try it, hope it will be fine with MD and MDd settings.