I copied the example listed above pretty much verbatim into a new VS2010 project and then fixed any missing references / compiler errors (using Unicode):

Code:
#include <windows.h>

int createWindow(HWND mWnd, HWND aWnd, char *data, char *parms, BOOL show, BOOL nopause)
{
    WNDCLASSEX wc;
    HWND hwnd;
    TCHAR className[] = L"MyWindow";
    HINSTANCE hInstance = GetModuleHandle(0);

    //Step 1: Registering the Window Class
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = DefWindowProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = className;
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, L"Window Registration Failed!", L"Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    // Step 2: Creating the Window
    hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        className,
        L"The title of my window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 240, 120,
        NULL, NULL, hInstance, NULL);

    if(hwnd == NULL)
    {
        MessageBox(NULL, L"Window Creation Failed!", L"Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hwnd, 1);
    UpdateWindow(hwnd);
    return 1;
}


The above works perfectly for me.

Note that you can only run the command once. The second time will fail because the RegisterClassEx function will fail, since you've already registered that window class. Ideally the registration of window classes should be done in the dll initialization, not for each /dll call, but this is just a proof of concept.

- argv[0] on EFnet #mIRC
- "Life is a pointer to an integer without a cast"