Which version of Windows do you have? What version of Windows do you have? They're both fine.
– FumbleFingersSep 13 '19 at 15:49
Thank you @FumbleFingers. By the way, despite using Which or What, the way I made the answer is also fine?
– João TeixeiraSep 13 '19 at 15:53
Yes, the way you've presented the question is fine. You should really have asked it on English Language Learners, but it was asked and (properly, imho) answered here on ELU years befotre ELL even existed, so I've voted to close it as a duplicate. It's not your fault if you didn't know about ELL and/or couldn't find the earlier question as asked here though.
– FumbleFingersSep 13 '19 at 16:12
You can use either, but I would say "what" unless I had previously provided a list of versions of Windows to choose from. "Which" is used to refer to a set of choices, for making a selection from that set or list. While the versions of Windows are a discrete list, not infinite, if I haven't provided that list, possibly a list that doesn't include every version of Windows out there, then I would say "what"? "What" is more inclusive of every version of Windows that might exist in the universe than exclusive to a specific set of choices available.
– Benjamin HarmanSep 13 '19 at 17:31
So, if I've, for example, already given the listener the choices of Windows XP, Windows 8, or Windows 10, I would say "which". But if I'm not limiting myself to any such list and want the answer no matter what it is, even if it's some ancient version of Windows nobody's used in 20 years, like Windows 95 maybe, like if that's what they're using, I want to know that, then I'd say "what."
– Benjamin HarmanSep 13 '19 at 17:39