Also, look for updated graphics card drivers on the Acer website. If you didn't update the drivers yourself, chances are you're using either the default Windows 7 driver which only supports minimal functionality, or an outdated version. If you want to use ddraw output (or direct3d when using a custom DOSBox build which supports this method) you should also run the latest DirectX 9 installer available from Microsofts website *.
* Some people say this is necessary, some say it isn't because the DirectX version included in Windows 7 is backwards compatible. I've had actual cases though where games or emulators wouldn't run properly or at all without installing the DX9 components. In any case, running the installer won't harm your system in any way.