 <p>You can't prevent the user from switching back because you've spawned a separate process. As far as the operating system is concerned it's as if you'd started the second one via it's desktop icon (for example).</p> <p>I think the best you can hope for is to disable the relevant menus/options when the second process is active. You'll need to keep polling to see if it's still alive, otherwise your main application will become unusable.</p> <p>Another approach might be to minimize the main application which will keep it out of the way.</p>