Just one other thing: I noticed that when I ran the example you provided, the one that works, the little balls raced on the preview screen but when running in normal saver mode they were very slow. I've seen this before and the reason for the difference is usually that the programmer making the saver drew a sized window for when running in preview mode. If you are doing that, I'm happy to tell you it isn't necessary. Your savers will work much better if you don't. All you have to do is set the parent/child relationship of the app window to the preview window, issue your preferred flavor of placement command, ie setwindowplacement, setwindowpos, movewindow, etc. which will also size your window, and that's it. Your 800 x 600 (or whatever) window will automatically be scaled by Windows to run in the space provided for it. So you just have to check for the /p parameter and if you get it, take the window handle that gets passed in the third parameter, use it with your app handle to set parent, set position, then just run normally. Your mod doesn't seem to include source so I can't see what it is you are doing in there, but it really doesn't need to be any more than that. (for preview mode. config mode is something else).