'↓を空のプロジェクト作って貼り付ければ動く。ディスク上のサイズは8KBｙte
'関数を自前で定義してインクルードファイル減らせばもっと減る筈。
Function wndproc(hWnd As HWND,Msg As DWord,wParam As WPARAM,lParam As LPARAM) As DWord
If Msg=WM_DESTROY Then PostMessage(hWnd,WM_QUIT,0,0)
wndproc = DefWindowProc(hWnd,Msg,wParam,lParam)
End Function

Dim wcx As WNDCLASSEX
wcx.cbSize = SizeOf(WNDCLASSEX)
wcx.style = 0
wcx.lpfnWndProc = AddressOf(wndproc)
wcx.cbClsExtra = 0
wcx.cbWndExtra = 0
wcx.hInstance = GetModuleHandle(NULL)
wcx.hIcon = LoadIcon(NULL,MAKEINTRESOURCE(IDI_APPLICATION))
wcx.hCursor = LoadCursor(NULL,MAKEINTRESOURCE(IDC_ARROW))
wcx.hbrBackground = GetStockObject(WHITE_BRUSH)
wcx.lpszMenuName = NULL
wcx.lpszClassName = "DEFAULTCLASS"
wcx.hIconSm = LoadIcon(NULL,MAKEINTRESOURCE(IDI_WINLOGO))
RegisterClassEx(wcx)

Dim hMainWnd As HWND
hMainWnd = CreateWindowEx(0,"DEFAULTCLASS","test",WS_OVERLAPPEDWINDOW Or WS_VISIBLE,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,0,NULL,GetModuleHandle(NULL),0)
ShowWindow(hMainWnd,5)

Dim Msg As MSG, Result As Long
Do
Result=GetMessage(Msg,0,0,0)
If Result=0 or Result=-1 Then Exit Do
TranslateMessage(Msg):DispatchMessage(Msg)
Loop