THE EASY WAY...Make your own .vpk addon!
Download L4D2 Authoring Tools:
http://download33.mediafire.com/cidjjbbkmttg/2lyldknykln/L4D2_Authoring_Tools_feb5.exeWatch this YouTube video tutorial on how to create your own .vpk addons:
I'm assuming you want to have players connecting to your server download the content you have on your dedicated server with good speed and reliability = "webhost" or "ftp server"
If you don't have the money for a server, watch this YouTube Tutorial on how to get 1GB ftp space
FREE
(I picked this one because the kid doesn't sound like an idiot)
After you've got your 'ftp host' setup, go ahead and download Filezilla, the 'Firefox' of ftp transfer applications:
http://filezilla-project.org/download.php?type=clientREMEMBER YOUR IP, USERNAME & PASSWORD. Write it down or save it as a server in FileZilla for quick access.Now lets get your server configured to force connecting clients to download addons or specific files
If you haven't already installed
sourcemod, you need to

:
http://www.sourcemod.net/dl.php?file_id=614&mirror_id=5Extract the contents of 'sourcemod' to your addons folder (C:\SRCDS\left4dead2\left4dead2\addons)
You will need this sourcemod plugin:
SM File/Folder Downloader and Precacher -
Info -
Direct DownloadExtract the contents of the SM File/Folder Downloader and Precacher to to your addons folder (C:\SRCDS\left4dead2\left4dead2\addons)
Remember to overwrite any existing files should there be any!
Now this is where it can be tricky:Open this .txt in notepad:
http://forums.alliedmods.net/attachment.php?attachmentid=25890&d=1208693958You will use this 'downloads example' file as a reference to making your own.
For this tutorial we will use a standard mp3 to replace the Midnight Riders finale music with "I'm on a Boat!"
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Gather all the files you want the connecting player to download upon connecting to the server.
Change the name of the mp3 to whatever is relevant to the sound you are trying to replace, for the Midnight Riders Concert, we will change the mp3 to "midnightriders.mp3"
You have to know where the sound files are so that you can replace them without corrupting other entities sounds:
Finale Music (Midnight Riders Concert);
sounds/music/flu/concert/midnightride.wav
your download.ini
sounds/music/flu/concert/midnightriders.mp3
~
or wav if you like. I'm still not quite to sure what the audio compatibility is with L4D2
~
sounds/music/flu/concert/midnightriders.mp3
Now you will need to upload the files to the 'ftp' or 'webhost' you got from the YouTube video.
Connect to your 'ftp' through FileZilla and recreate the file directory for the custom audio (create all the folders inside another folder to keep the directory link the same):
left4dead2/sound/music/flu/concert/midnightriders.mp3
The same setup goes for models and maps:
left4dead2/materials/models/v_models/eq_molotov/v_eq_molotov_bottla.vtf-
left4dead2/materials/models/v_models/v_eq_molotov_bottla.vtf.bz2
PAY ATTENTION TO THE V/W_MODELS FOLDERS, THERE IS A DIFFERENCE!
left4dead2/materials/models/w_models/eq_medkit/w_eq_medkit.vtf
Just refer to the "download example" txt file that is included with the SM File/Folder Downloader and Precacher!
This is where people were having trouble-----> sv_downloadurl
Register for an account at
http://www.e-frag.co.uk/register.php
Follow the instructions after you register at e-frag, or the 'sv_downloadurl' site.
After completing the steps, you are sent an email with the proper downloadurl to use to download from your 'ftp host'
Example:
sv_downloadurl "
http://svdownload.e-frag.co.uk/users/Knappy/left4dead2"
Remember how those files in the downloads.ini started with sounds? This is where e-frag tells it where to start, so make SURE YOUR FILES ARE IN THE CORRESPONDING PLACES WITH YOUR SERVER!
DON'T FORGET TO UPLOAD YOUR ADDON TO YOUR FTP HOST!