I don't think it's a PATH related problem, because the linker is able to find the other *.obj files that are created by the compiler. Also, upon inspection of the folder where all *.obj files reside, there is not one for options.obj (while there are *.obj files for main.cpp and options_moc.cpp (i.e. main.obj and options_moc.obj)).

Furthermore, using the 'Rebuild' command (instead of 'Build') causes the program to be built correctly.

The reason we are using MPC (as opposed to QMake) is because we have a need to integrate IDL files (CORBA) into our application, thus we need to specify the Custom Build Steps for the IDL files, which MPC can do quit easily. As far as I can tell, you cannot specify to QMake how to create Custom Build Steps for other types of files, such as IDL files.