The community is also a great place to check out. Try these places for help from other users:
Downloadable content will not be listed as a separate entry in your Steam games list.
To view the additional content for this game that is registered to your account, please do the following:
Any DLC that is listed in this window has already been downloaded and integrated with Borderlands 2. If you are having trouble accessing this content, please contact Borderlands Support for specific instructions for locating the content in-game.
If you're encountering issues with launching Borderlands 2, make sure everything installed smoothly.
Exit Steam entirely.
Browse to your Borderlands 2 installation folder (Usually C:\Program files\Steam\Steamapps\common\Borderlands 2\)
Run the following installers:
Reboot your computer and test any issues again. If you continue to encounter any issues, contact Borderlands 2 support.
If the above does not resolve the issue and you are running Windows 7 or Windows Vista, please complete the instructions in our Windows 7 and Vista Troubleshooting FAQ.
If you are running in Windows XP, take the following steps: