WereSquirrel: The Steam version of King's Bounty just got broken by a sneaky patch. Multiple people report that it makes the game crash for them. I imagine it's to insert promotional content for their exceptionally bad sequel.
I sure hope that this same patch won't be pushed to GOG, or that GOG will give us access forever to the previous versions. They've fallen into the bad habit of giving us access only to the latest files, as if this is what classic gaming was about.
To be on the safe side just back up your offline installers. That way you'll always have the version you want to reinstall.