For single player, only the paks are needed (pak0.pak, pak1.pak,& pak2.pak on mine, might be different for different versions of q2), for multiplayer, you might want to have the players folder too. It'll work without, but you'll get some warnings about missing images, and won't see them on the scorelist. There are also couple files in the pics folder that are needed, but those come with quetoo, and are copied into the basedir, when you set it in the launcher.