While the latest Dungeon Keeper may not be at all what you want, a free-to-play mobile game with microtransactions up the wazoo, hey, what's the harm--the original still exists, right? Indeed it does, and now it's briefly free for everyone to download and play (no microtransactions, either) on GOG.
To snag your free copy, simply mosey on down to GOG to claim one. Due to demand, it'll take a short while for the 'purchase' to process. You only have until 2:59am Pacific on Sunday, February 16 to get in, but the copy will stay on your account forever.
It's all to draw attention to GOG's big Valentine's Day sale, which offers sizeable savings on games including System Shock 2, the new Rise of the Triad, Trine, Syndicate Wars, Trine 2, and Dungeon Keeper 2.