Well, if you are trying to multi-task, as in letting the user alt-tab so he can do something else, then you shouldn't be trying to get exclusive control in the first place. Then, I really don't think anyone is going to want to run two CPU hungry fullscreen games at once. And if they do, I say let them. If they run out of memory, it is their own problem. But, I think you should allow them to run another program, even if it is another full screen application like yours. I don't even think you need to detect it, rather when your application is reactivated, recreate the fullscreen part, though the window just needs maximized. So, my opinion is just to be as compatible as possible and don't try to take over the computer.

Also, I think that unless your program itself starts another one, I don't think it will start by itself. If it does, like maybe internet popups or something like it, the screen will probably keep the same resolution etc... that you have it at and "tab out" of your application, just like if the user had done it, then giving focus to the "new" application, full-screen or not.

I see....... That changes things a little bit. I'm glad you explained that to me. The problem I see is that windows itself automatically gets out of an app or game when another window takes the focus. I think you might could somehow grab the "lost-focus" message, (don't remember what it's called), and somehow react to it. I have heard of message hooks as well that I think allow you to get other windows messages, but they might have to be your own windows. That is about all the help I think I have for this situation. I tried though. Post any results you get. I'd like to see.

Try the NeHe base code. Provides a function to open a window in fullscreen or windowed ;)