Ok many thanks. Have resolved the problem by first doing a nmake distclean then a qmake -project to generate another .pro file. This then compiled but generated some unresolved external references. I fixed the linker issue with ensuring
win32:LIBS += C:\Microsoft-Platform-SDK\Lib\Ole32.lib was included in the .pro file which was a library required by the linker. Everything compiled and linked clean and .exe file executes as expected.

Many thanks, Mike