Disable mouse and keyboard input

You can disable the window, by calling the method CWnd::EnableWindow(BOOL bEnable), this way your window will not accept any user input, both mouse and keyboard.
This approach is the easiest one, but it make your window not able to process any kind of user interaction: you will be not able to minimize the window to the taskbar, to move the window by dragging its title bar, and so on.
If your window is dialog based and your target is to disable all the controls on the client area of the window, the best solution is to place all the controls on a child window (i.e. declared as WS_CHILD and without title bar nor border) then place that child window on the client area of your main window and then enable/disable the child window. This way the user will be not able to interact to the controls on the window, but he will be able to move the window on screen, minimize and maximize it, and so on.