The mkspec says win32-msvc. Is this the correct one? I am building a 32 bit app with 32 bit Qt. Is the following line correct for the qmake.conf there? It compiles and runs with that line, but I don't know that if it's incorrect it just ignores it. I can't test it because I don't have that older architecture on my development PC. It's a build for one of the users of my application. QMAKE_CFLAGS_RELEASE = /arch:SSE