Well I did a little searching and found a downloadble, free, massive multiplayer online adventure games called Runescape.
Here's a link to it so you can check it out before deciding anything :
http://www.runescape.com/runeinfo.html
It's pretty good actually. Maybe it doesn't have the best graphics and the battle system could be better, but I liked it. You can create your character and choose which world to play in. You interact with others (saying what you want) trade or fight with them. You can send messages to others. There are quests you have to carry out and other things like that. It may not be as good as Baldur's Gate or Diablo, but it's something everyone can get easily and for free.
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