(Method: Click your original file, and then click on the right key to select 'Properties' from the pop-up menu, you can see the version number of the files) If your original file is just corrupted but not lost, then please check the version number of your files. If you know MD5 value of the required files, it is the best approach to make choice I haven't a problem i'm just sharing how i solved my problem in this specific case.Tip: How to correctly select the file you need Just wanted to share my experience, had the same problem ON LINUX (ubuntu), i got the game from a friend (pen drive, to avoid download), i put it in the right folder and tryed to launch it on steam, steam identified my local files and avoided download but then this error happened, steam 'automatically gives permission' when downloads the game, but steam haven't downloaded it so after some time i remembered to give permission to the folder, if this is your case just give permission to the entire folder, on terminal type: sudo chmod 777 -R FolderAdressHere and try again. Again, I don't have to do this for all Steam games, just this one and one or two others. When I play L4D2, I have to close Steam from the windows task tray, and then right click on the Steam shortcut and 'Run as Administrator.' L4D2 then runs perfectly for me. I have my games installed on a separate, larger HDD that is on a different drive letter SSD where my OS resides. I had a similar issue with the 'unable to launch - unknown error.' This error only occurs on a handful of games including L4D2. Linksys Wrt54gc Ver 2.0 Firmware Update on this page. If not, shut off unnecessary programs (GameBooster might help. Same actions as Step2, and run in compatibility mode. I always have L4D2 run through admin and it works just fine for me. Hola amigos tengo un problema en el autoupdater es que me sale unable to execute command left4dead2.exe -steam -game left4dead2 - novid (2) POR FAVOR SEAN RAPIDOS DE RESPONDER QUIERO JUGAR EL JUEGO!!! Your PC is unable to read the files it needs to run. You need to register left 4 dead 2 launcher.exe manually: run command. 1) Go to the.exe (C:>ProgramFilesx86>Steam>SteamApps>Common>Left4Dead2>left4dead2.exe) 2) Right click>Properties>Compatibility(Tab)>Check 'Run as administrator'>Apply/OK 3) After you tick the 'Run as Administrator' box, apply the settings and run the game through Steam (don't click on the.exe itself)! I have no idea why, but try running the game as administrator.

Unable to execute left4dead2.exe