tfishell: More GOG games support Windows 7 than 10 (though the difference isn't that big, afaik). I'd suggest keeping the old XP machine around if you want to play original old games; I've been toying with the idea of buying an old Windows 98 machine eventually, to play some of my childhood games in their original form.
As an aside,
always check the "Works on" section and system requirements to make sure you can qualify for a refund (that you're running a supported OS and meet the system requirements), in the case that you can't get the game running and Support can't help you.
Jo6Pak: Thanks for your input. My concern regarding older versions of Windows (especially XP) is that GOG may optimize the old games to actually run better on a newer O/S. I'm new here, so not sure what all they do when repackaging the old ones. I no longer have any of the original disks and not inclined to search them out, so I'd be getting the games from GOG.
Well I think GOG
generally just applies tweaks and fixes (depends on how well they expect a game to sell, thus how much they expect to make back), and a portion of GOG games officially supported on new OSes may still have issues on those new OSes,
and most of the non-new games here are supported by WinXP, so I
think I can safely advise you to play non-DOS Good Old Games games on older machines. GOG games that use emulators may be another thing (depending on the DOS game), because those can need a lot more CPU power to run well (since the computer is running two OSes basically); you'll see GOG reviews about DOSBox slowdowns happening when there's a lot on-screen at once. I don't know if this applies to games that use nGlide.
If you were to play GOG's release of Populous 3 or Interstate '76 or Gorky 17, you'd probably want a WinXP machine for those.