Running the game on a brand new Dell XPS 27 with Windows 10. I try and get the game to run within a window rather than full screen but it ignores the change in Options. All I want is to be able to switch between the game and other tasks without shutting it down.

Alt + Tab isn't working?

1) Check if your Documents/Witcher 3 folder and all the files inside it is not read only.
2) Have you got switchable graphics? Check if your game is running with the high performance chip, just in case.
3) Try ALT+ENTER.
4) Have you tried borderless windowed full screen?
5) If you just want to switch between tasks, you can use ALT+TAB as Ritualisto suggest.
6)

Many thanks Ritualisto that worked. The manual that comes with the game is pretty basic and does not detail that. Do you have another source of additional information for this or other problems I may encounter. I have to say that i am finding the control interface difficult to master buy am persevering. Many thanks for taking the time to reply, Ritualisto's keystroke combo solved that problem. Pls see my reply to him - likewise if you have any other sources for additional info it would be appreciated.

Alt+Tab is a Windows hotkey. It will work on all Windows systems with all tasks which are open.
Sorry I don't have an advice for your control interface problem. Perhaps try to play the game with a game pad.

Thanks anyway, appreciate your time in responding.

Very good!
Enjoy the game ;)

PS: If you want to know more about Windows hotkeys, you can check this article: http://windows.microsoft.com/en-us/windows-10/keyboard-shortcuts