You have couple of options how to set your download location for the HTC Vive. Follow this guide how to successfully finish the different ways for this typical question.
Step 1. Go to Steam Library
Step 2. Open Steam Settings
Step 3. Go to Downloads
Step 4. Steam Library Folders
■ If you have more locations and they all have a steam application directory the Steam VR may not give you an option to change the location.
■ You will have to physically disconnect the drive so you can get around it.