Good selection of titles, and it reminds me too, I'm sad my Heretic disc went missing years ago in some move I think. I bought it when it came out, then went and got the fuller version with the Serpent Riders. Miss it, sure I could just go get the WAD files but I don't. I'm surprised GoG hasn't thrown that up there yet unless there's some contract deal maybe with Raven? I know Raven had their name on Hexen, but not Heretic.
Also CIV3 came out in 2001 and was for win98/98/me/2000. It was developed just before XP so it wasn't on the box as native to it. It'll work.