http://en.wikipedia.org/wiki/Call_of...s_of_the_Earth
http://www.callofcthulhu.com/gameinfo/cocfaq.html
Rather more recent than our usual fare, but MobyGames confirms that the developers have gone out of business and the minimum specs are pleasantly low for a game released in 2005. I'm actively looking for a used copy, so once I get my hands on one I'll see how far down I can compress an ISO image.