You should install the latest version (Windows 11) if your hardware supports it, otherwise Windows 10. Do a backup first to a location that will be accessible after the upgrade, upgrade, then do a restore.
Basically any other operating system. Windows 7 is a serious security risk today. Rock (Linux), Windows 10 or 11 are equally fine. Your Roon library, favs and edits you get back when you restore your new Core’s database from a backup which should happen on a regular basis today.