Not sure what happened since last few updates Windows 10 or GoG wise, (all my games ran fine in November, last time I had time to game), but all my games from Outlaws to Wizardry 8 minimize upon launch now. Refuse to maximize/full screen and just go back to taskbar.

I've tried upgrading nglide to 2.0 (1.04 is default distributed with GoG), using alternative glide wrappers like dgVoodoo, playing with resolutions, not using glide/3dfx, upgrading AND downgrading gfx drivers, updating Windows, reinstalling all games in question, disabling any and all background applications/services.

Only way to get any of my GoG games to run is to drop my desktop resolution to 1280x720 (my monitor native is 2560x1440) AND forcing "640x480" option in compatibility settings (although this varies from game to game, some just require desktop @ 1280x720, and some require the compatibility tick as well)

What happened in the last month? I haven't had time to run any GoG games since November, but all of them ran fine. Now everything just minimizes or is stuck at 720p?

Windows 10 @ NVidia 1060 GPU with latest drivers and updates all around right now.

Try reinstalling the latest graphics drivers. Some have reported that some Windows 10 update has replaced graphics drivers with some default ones which don't work well.

(GOG forum ate my earlier reply.)

Sounds to me like another program might be stealing the focus/minimising the games. Did you install anything else since November, like remote management software, maybe?

It might also be worth checking your Task Scheduler to see if there's anything trying to launch when this happens.