You definitely should continue to use Windows 7 (for games in an offline capacity). Nothing wrong with that and it's exactly what you should be doing for gaming with old games. I legally own Windows 7 Ultimate and Windows 10 Pro, and use both of them for playing my old (and wonderful) collection of games. It's the same thing you would do either with just owning a Gameboy/N64/PS1/PS2, etc, or for the desktop case, trying to emulate old hardware on X platform. The former here is more applicable than the latter of course, but both are perfectly valid when speaking about systems used in an offline capacity.