you only need 3.17
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FAQ: Patching Sid Meier's Civilization 4: Beyond the Sword[/size]
Q: I logged into the Beyond the Sword lobby and received a message that I need to download a game patch before I can play online. Should I download the patch from within the lobby?
A: No. Although you have received this message because your game is not currently up-to-date, unfortunately
the patch does not download properly in the Civilization 4 Lobby.
Q: Well, then how can I patch the game and play online again?
A: First, close your game by exiting the game or pressing CTRL+ALT+DELETE and using the "END TASK" function to close Civilization 4. The particular patch that you now need to download depends on where you purchased the game.
Q: Where should I get the patch if I bought Beyond the Sword from a store?
A: Click
here to download the Beyond the Sword 3.17 Patch.
Q: Where should I get the patch if I bought Beyond the Sword from Direct2Drive?
A: Click
here to access Direct2Drive's patch directory. Search for the Beyond the Sword 3.17 Digital Distribution patch and download it.
Q: Where should I get the patch if I bought Beyond the Sword from Steam?
A: Steam should have automatically patched your game before it loaded. If you bought Beyond the Sword from Steam and cannot play multiplayer, contact them using their Support page. Most likely, you will need to fully reinstall Beyond the Sword to fix this (rare) problem.
Q: Where should I get the patch if I have an illegal copy of BTS?
A: Click
here to download a compatible patch for illegal copies of Beyond the Sword.
thanks to JbAdams for these tips!