You can move the Phobos content onto a different drive attached to the computer onto which you installed Phobos. You cannot move the content onto a different computer as Phobos is only authorised for use on the computer that the download was performed on.
To move the content to a different drive attached to the same computer, you will need to move the Patches, Presets and Samples folders and then edit the following file:
username/Music/Spitfire Audio/Settings ("username" represents your home directory)
Open the spitfire.properties file in a text editor and you should see something like this:
This file shows Phobos where to find the content that it needs and can be directly edited if the folders have moved for any reason.
If the above does not work or your Patches, Presets or Sample folders are missing or incomplete, please reset the library from the Spitfire Audio App and download Phobos again.