Redmond, Wash. - Microsoft (NASD: MSFT) on Thursday announced that it plans to upgrade its Games for Windows -- LIVE online gaming service, the Web community for its slate of PC games, and begin offering downloadable game content. While the free service already offers gamertags, voice and text chat, matchmaking and leaderboards, Microsoft in early December will add downloadable game trailers, demos and add-on game content like extended chapters and new characters for PC games.