Title: Left 4 Dead 2 
Genre: Action 
Developer: Valve 
Publisher: Valve 
Release Date: 17 Nov 2009 
Languages: English

Compressed Game Is 1.97GB - After Decompression Is 8.03GB

SYSTEM RE:

Operating System: Windows 7 / Windows Vista / Windows Vista64 / Windows XP 
Processor: Intel Pentium 4 3.0 GHz 
Memory: 1 GB for XP / 2GB for Vista 
Hard Drive: 7.5 GB Free 
Video Card (graphics): DirectX 9 compatible video card with 128 MB, Shader model 2.0. ATI X800, NVidia 6600 or better 
DirectX: 9.0c 
Sound Card: DirectX 9.0c compatible sound card

The Recommended Requirements For Left 4 Dead 2:

Operating System: Windows 7 / Windows Vista / Windows Vista64 / Windows XP 
Processor: Intel core 2 duo 2.4GHz 
Memory: 1 GB for XP / 2GB for Vista 
Hard Drive: 7.5 GB Free 
Video Card (graphics): DirectX 9 compatible video card with Shader model 3.0. NVidia 7600, ATI X1600 or better 
DirectX: 9.0c 
Sound Card: DirectX 9.0c compatible sound card

INSTALL:

1) Disable UAC on Windows 7 And Windows Vista

2) Extract To Short Paths Like C:/Games Or D:/Games 
3) Go To The Extracted Folder And Run the SETUP.bat File 
4) Wait Till Finished Rebuilding. Then Start The Game From Your Desktop.

# Change Your Ingame Name And Language With "L4D2 Control Panel" 
# If you have any sound trouble, like Crackling sounds in between the game or the audio doesn't syncs or similar to that. All you have to do is :

-> Open Console and type the following Command :

snd_rebuildaudiocache

And then wait for few mins (10-15mins), Exit and Restart the game.

Multiplayer Gameplay Available Through Garena. 
And 
Cracked Servers Via The Internet.

Playing Online Through Garena

Installing Garena 
1. Go to http://www.garena.com/ then click Download Garena. 
2. Click any mirror under your preferred language to download. 
3. Start Garena_setup.exe. 
4. Follow the instruction and finish the installation.

Registering Garena Account 
1. Start Garena and click on Register when Garena login window show up. 
2. Fill in all the form accordingly then click Submit.

Setting Garena for Left 4 Dead 2 
1. Start and Login your Garena. 
2. Click Game -> Left 4 Dead 2 on the left sidebar. Select your Country Region* and double click room to join. 
3. Click Settings. 
4. Click the Browse button. 
5. Navigate to your Left 4 Dead 2 folder (By default: C:\Program Files\Left 4 Dead 2) and select left4dead.exe then click Open. 
6. Nothing Required at Game Bootstrap Parameters box. 
7. Click Update! 
8. You can now click Start Gamebutton to play Left 4 Dead.

And you want left 4 dead 2 V2.1.3.4 update? or transform to Left 4 Dead 2 V2.0.2.7 Full-Rip  to  left 4 dead 2 V 2.1.3.4 ?

Go this link And follow Gani's Instructions http://gaming-extreme.com/topic/4-left-4-dead-2-nonsteam-guide-updates-patches/

for full update