Error: A Command with that name already exists.
Description: This error usually pops up from Visual Studio when there is a corrupted add-in or extension added into VSPackages.
Solution: Identify, remove and reinstall the extension. And run the following command Devenv.exe /ResetSkipPkgs from Visual Studio Command Prompt. /ResetSkipPkgs clears all options to skip loading added to VSPackages by users wishing to avoid loading problem VSPackages, then starts Visual Studio.
Edit: How to remove Addins from Visual Studio.
Open path – C:\Users\username\Documents\Visual Studio 2010\Addins and remove the necessary files.
Then type and run devenv /resetaddin following command from Visual Studio Command Prompt.