So when I press Alt + Enter, all I get is the black box with numbers at the top right corner. The fullscreen mode works fine. I've already played with compatibility versions. What can you do to access windowed mode? My PC has a Radeon 7850M + i7-3770T with the latest drivers. Happy Mapling!
http://forums.maplesaga.com/index.php?threads/unable-to-access-window-mode.4869/ I've posted my fix to this problem in this Topic, i hope it works for you aswel!