"const wchar_t is incompatible with parameter of type "LPCSTR"

 

MessageBox(NULL, L"TEST", L"TEST", MB_OK);

 

You may get this error if you "Use Multi-Byte Character Set", 

"const wchar_t is incompatible with parameter of type "LPCSTR"

 

In this case, use TEXT("") instead of L""

MessageBox(NULL, TEXT("TEST"), TEXT("TEST"), MB_OK);