Such a Linux OS can fit on a CD, with multimedia applications, games, word processors and browsers. Knoppix, SuSE Linux (the evaluation version) and others I don't know about. Whether you like them or not, they clearly prove that you can get a decent interface without wasting space with useless rubbish. And Mac OS X may be quite big, but it provides much more useful and innovative features than that bloated Longhorn crap.