Installing L4D2 Add-ons for Windows Step 1: Download the add-on. All downloads are in .zip format. (You need to open the .zip archive to access the .vpk file.) If you can not open or extract the .zip/.rar file, download and install winrar for free. Step 2: Install the add-on. Double click the .vpk file to automatically install the add-on. Or, Right Click > Open With > Browse > \Steam\steamapps\common\left 4 dead 2\bin\addoninstaller Manual Install Copy the .vpk to your L4D add-on directory. If this folder does not exist, create this folder. \Steam\steamapps\common\left 4 dead 2\left4dead2\addons\ Step 3: Enable the add-on. Once you have successfully installed your maps you can enable or disable them at any time. 1. Open L4D / L4D2. 2. Click on the 'Add-ons' option to load all installed addons. 3. From here your list of addons will be displayed. Check / uncheck addons to enable / disable. You can remove add-ons by deleting them from your /addons/ folder. Installing L4D2 Add-ons for Mac Some add-on's might have file-names too long for the Mac to recognize. In this situation try renaming the add-on to a shorter file-name and try again. Manual Install Copy the .vpk to your L4D add-on directory. If this folder does not exist, create this folder. \left4dead2\addons\