And here I am still regretting giving away my old Win98SE machine when I had to downsize from one apartment to one room. Wish I'd have kept it anyways. You'd be amazed what does actually run on something like that (the internet, Firefox 1.0 or maybe even 2.0 lol). Not WELL, but it runs.
Yeah, GOG is the best option, 9/10 times. You can always DL the install file from the site, then copy it to a drive/disc. Outside of EMP, flood/fire, or a bad drive (replace those regularly), you're golden. Same with Bandcamp for music, Gutenburg for ebooks, or DriveThruRPG for... PnP RPGs.