关于API windows的程序

#include<windows.h>

int WINAPI WinMain (HINSTANCE hInstance,
                    HINSTANCE hPrevInstance,
                    PSTR szCmdLine,
                    int iCmdShow)

{
    MessageBox (NULL,TEXT("Hello word!"),
        TEXT("HellMsg"),0);
    return 0;
}

为什么在我的vc6.0里编译时没有出错，但连接时会出错呢？
错误为：LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/10.3.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.