Unfortunately the whole fullscreen D3D / focus window thing is a bit of a mystery to me... I'm currently creating multiple D3D devices for multiple gfx cards (I'll ignore the multi-head stuff as that should be trivial). All running in a single thread. 1) All my created devices are attaching to a SINGLE focus window. This isn't my main app window, it's just one I create and give focus. 2) The WndProc for the focus window handles nothing except WM_ERASEBKGND, to ensure it is ignored. Seems to work. But that's the bit I hate. I'd like to KNOW that it should work, or recode it the proper way. The next phase is to create each D3D device in it's own thread. In this case they will all need their own focus windows (or do they?). The docs seem to suggest that is OK, you just give each the focus in turn as you init fullscreen mode. Sounds tricky to handle lost devices though... Anyone like to point out where I might be screwing up before I waste too many nights of this?