Something to try before forcing a power cycle if your computer freezes is to restart your graphics drivers. This neat Windows 8 and Windows 10 tip (sorry Windows 7 users) works with any graphic solution. Press Win+Ctrl+Shift+B together and your graphics display will blank then and after a brief moment, will reappear and, with a little luck, allow you to keep on computing. Of course this only works if the problem was originally your graphics freezing. Still, something to remember.