Code:
#include <windows.h>
//Controls
HWND Window1;
HWND Button1;



LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

int WINAPI
WinMain (HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nFunsterStil)
{
    MSG messages;            /* Here messages to the application are saved */
    WNDCLASSEX wincl;        /* Data structure for the windowclass */

    /* The Window structure */
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = "Window1";
    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    wincl.style = CS_DBLCLKS;                 /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;                 /* No menu */
    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default color as the background of the window */
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;


    //Window1
    Window1 = CreateWindowEx(
           0, "Window1", "Tic Tac Toe!", WS_OVERLAPPEDWINDOW, 300, 300, 300, 150,
           HWND_DESKTOP, NULL, hThisInstance, NULL);
    //Button1
    Button1 = CreateWindow(
            "Button1", "Exit", WS_VISIBLE|WS_CHILD|BS_DEFPUSHBUTTON, 10, 10, 50, 25, Window1,
            NULL, (HINSTANCE) GetWindowLong(Window1, GWL_HINSTANCE), NULL);
    ShowWindow (Window1, nFunsterStil);
    //Messages


    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK
WindowProcedure (HWND Window1, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)                  /* handle the messages */
    {
        case WM_DESTROY:
            PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
            break;
        default:                      /* for messages that we don't deal with */
            return DefWindowProc (Window1, message, wParam, lParam);
    }

    return 0;
}
Please Help!!