If you are experiencing technical issues with installing Borderlands 2 or within the game, please complete the following:
First, please verify the GCF for this game as outlined here:Note: Files may fail to verify. This is normal and can be ignored.
Then test the issue.
If you still have difficulty, you may also need to manually run secondary installers required by this game.
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 the issue again.
If the issues persist, please see the following FAQs:
If you continue to experience technical issues with Borderlands 2, please contact 2K Support. Steam Support is unable to provide technical support for 3rd party games.