Ошибка прав доступа

#include "windows.h"
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hinstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int noCmdShow) {
    HWND hMainWind=NULL;
    char szClass[] = "MyClass";
    MSG msg;
    WNDCLASSEX wc;
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hinstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.lpszMenuName = NULL;
    wc.hIconSm = LoadIcon(NULL,IDI_APPLICATION);
    if (RegisterClassEx(&wc)) {
        MessageBox(NULL, "Cannot register class", "ERR", MB_OK);
        return 0;
    }
    hMainWind = CreateWindow(szClass, "A smth", WS_OVERLAPPEDWINDOW, 50, 50, 500, 500, HWND_DESKTOP, (HMENU)NULL, (HINSTANCE)hinstance, NULL);
    //UpdateWindow(hMainWind);
    if (!hMainWind) {
        MessageBox(NULL, "cannot create maine window", "err", MB_OK);
        return 0;
    }
    ShowWindow(hMainWind,noCmdShow);
    while (GetMessage(&msg,NULL,0,0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam) {
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    switch (uMsg) {
    case WM_PAINT:
        hdc = BeginPaint(hwnd,&ps);
        GetClientRect(hwnd,&rect);
        DrawText(hdc,"Hello World",-1,&rect,DT_SINGLELINE|DT_CENTER|DT_VCENTER);
        EndPaint(hwnd,&ps);
        break;
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd,uMsg,wParam,lParam);
    }
    return 0;
}

if( ! RegisterClassEx(&wc) )