Info: Windows 10 Status and yes there'll be no Win 9.

[Mobhack]

It may be that you don't yet have video drivers for Windows 10 that will support 256 colour modes, or that the video card manufacturers think its an outdated MSDOS mode, so not worth writing. Microsoft themselves may have removed any requirement to support the mode as "obsolete" - same as modern windows versions (and video drivers for modern monitors) wont let you select 640 mode. Likely in the future even 800 mode might fall by the wayside as well, wouldn't surprise me.

So windowed mode using desktop resolution is really the best way forward. Its actually faster for modern day cards to do full colour display and convert the 256 colour palette into that mode on the fly, than to use a native 256 colour mode. It used to be the other way round in the DOS and early windows days of course!.

Plus windowed mode will work in collaboration with the other open windows programmes, allowing task switching without the risk of Windows messing up the palette when you try to return to the game, leaving you with a psychedelic display.

So, I'm not too worried about 256 colour full screen paletted MS-DOS mode not working. Its a legacy mode from the 1990/2000 era and 4:3 aspect CRT monitors.