I've just updated a small guide in the camelotserver.de forums, to make things easier for you guys, here's a copy of it:

Simply visit the download section of http://daoc.goa.com and download either the Shrouded Isles or the Trials of Atlantis installer. This small program will help you installing the entire game in its latest European version then.

ATTENTION: Note that you don't have to install the Shrouded Isles or Trials of Atlantis expansion in case you want to get the newer DAoC: Catacombs instead! Every expansion is a stand-alone client that includes all previous clients' functions; that means you have to download only ONE of them!

To get the most recent DAoC expansion, Catacombs, download either the Shrouded Isles or Trials of Atlantis installer (it doesn't matter which one), double click it, then select a folder and click "Install". As soon as the download process has started abort it by clicking the "Cancel" button. Search for the file update.dat in the game's folder and edit it using Notepad. Replace the text found in the file with these three lines (there mustn't be any empty spaces behind each of them!):

Mythic Patch
patch.camelot-europe.com:1280/updates/english/catacombs/mpatch.dat
patch.camelot-europe.com:1280/updates/english/catacombs/mpatch.dat


Now click the camelot.exe file to start downloading the Catacombs game client.