monitor

The error is telling you that your declaration of MonitorFromWindow conflicts with the prior declaration. The prior declaration in Winuser.h declared the function with extern “C” linkage, is __declspec(dllimport) and has the __stdcall calling convention. You should remove your erroneous declaration and use that from the header file. 15 solved Windows7.1 SDK: C2373: “MonitorFromWindow” Redefinition