Data Error: Cyclic Redundany Check (Need Halo Download...)

[Big Country]

Did you try downloading the dedicated server maps from the Microsoft web site? It says they are the same maps as in the retail version. You might find the file you are looking for in there.

Halo_DS_Maps_1_02.exe
This self-extracting file includes the multiplayer maps required to run Halo Dedicated Server. You only need to download these once. If you already have the full retail Halo game installed on your server, you do not need to download the maps at all; the server will use the maps that were installed by the game.

http://www.microsoft.com/games/halo/downloads.asp