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You play N64 online by finding an emulator, once you have found one that is reliable you just gather game files and load them on to it. .j. Vizzed Retro Game Room has an emulator: http://www.vizzed.com/playonlinegames/index.php?ref=108749
apparently nowhere because this world is too slow to play age old games on the computer. Vizzed Retro Game Room is actually great for playing games, any game boy and even Nintendo 64. You can find sapphire at: http://www.vizzed.com/vizzedboard/retro/game.php?id=10647&ref=108749 The only thing you will need is a simple plugin for your browser. I personally use it, and no viruses. However, Norton may detect the Nintendo 64 plugin as a false positive, but it IS indeed virus free.
Go to http://www.vizzed.com/playonlinegames/index.php?system=gba&ref=108749 to play every GBA game ever made, online, completely free! Only thing is, you need to register on the site in order to save your games, and, you need to download a plugin (takes like 30 seconds). Unfortunately, the site does not currently support Mac, but you can play on any version of Windows XP and up.