WinArch 10.
Well....At home I use 8.1 x64 still because I have not put the time into hunting up all the installers for the gajillion programs i have installed. At work I use 10 pro x64, 7 pro x64, and XP, depending on what needs doing....and though it probably doesn't matter for this thread, a good bit of windows server, various editions.
If you read the question, it clearly asks the OS of the computer you play w3d games with
And who's to say I don't game on all of these?? Kidding