C++ is case-sensitive. The function should be WinMain. not WinMAin.
The signature of your function looks strange. Normal is: int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevIns, LPSTR lpszArgument, int iShow)
What compiler IDE do you use?
Those kind of errors better be detected quickly as they can cause serious problems later. Sometimes it can get a little harder but don't loose focus. If you find it a problem for you, you can always use some code security program. I have heard of called checkmarx. Not sure of their cost but sounds nice.
Anyway. good luck!
Ben.