Installation:
1- Download :hldsupdatetool.exe
This tool is used to download, update and run the dedicated Source server.
Install hldsupdatetool in a folder eg. C:\HLServer

2- Now you will need to download the files for your dedicated L4D server:
Start <>CMD
Type: cd.. until you get to the root (C:\)
Type: cd HLServer
Go to explorer and create a new folder, eg. in C:\ L4D_Server
Back in CMD type: hldsupdatetool.exe -command update -game l4d_full -dir C:\L4D_Server
[This may take a while.]

Configuration:
3- When it's ready you need to crack the server:
-In L4D_Server\l4d\bin\ - Rename "steamclient.dll" to "steamclient.dll.old"
-Download REVOLUTiON's Steam Emulator [get Rev-Emu & see NOTE below]:
-Extract the contents of Rev-Emu to C:\L4D_Server\l4d and move steamclient.dll into C:\L4D_Server\l4d\bin directory
-Open "rev.ini" and edit "SteamDll", like this: SteamDll=C:\L4D_Server\l4d\bin\Steam.dll.old
and "ClientDLL" to this: ClientDLL=steamclient.dll.old
Set "CacheEnable" to "False" and "SteamClient" to "True". Edit "SteamUser" and "PlayerName". Save & Exit.

4- You will want to setup the server.cfg in L4D_Server\left4dead\cfg
Input your own info for CHANGE ME.

Example server.cfg:
--------------------------------------------------------
//BASIC INFORMATION SETUP

hostname CHANGE ME
rcon_password CHANGEME
sv_password ""
sv_contact "CHANGEME"

//BASIC GAMEPLAY SETUP

mp_disable_autokick 1
sv_allow_wait_command 0
sv_alltalk 0
sv_alternateticks 0
sv_clearhinthistory 0
sv_consistency 1
sv_pausable 1
sv_voiceenable 1
sv_cheats 0
sv_infinite_ammo 0
sv_forcepreload 1
//sv_gametype coop //versus or coop

//BASIC CONNECTION SETUP

hostport 27016
sv_lan 0
sv_region 0
sv_allow_lobby_connect_only 0
//sv_allowdownload 1
//sv_allowupload 1
//sv_downloadurl ""
//net_maxfilesize 64

//BASIC SERVER LOGGING
sv_log_onefile 0
sv_logbans 1
sv_logecho 0
sv_logfile 1
sv_logflush 0
sv_logsdir logs

//ADVANCED CONNECTION SETUP
setmaster add 213.239.209.221

//ADVANCED SETTINGS
sv_pure_kick_clients 0
//sv_steamgroup
//sv_steamgroup_exclusive 0

//EXECUTE
exec banned_user.cfg
exec banned_ip.cfg

//TWEAKS
//sv_minrate 10000
//sv_maxrate 25000
sv_maxcmdrate 100
//rate 30000
cl_cmdrate 30 // LAG fix
cl_updaterate 20 // LAG fix
rate 20000 // LAG fix
sv_minrate 5000 // LAG fix
sv_maxrate 8000 // LAG fix if you have less than 120 kb upload bandwidth