well, he would move the files off his desktop once he is finished with them, its just a temporary thing. he was concerned with using up a lot of the main SSD hard drive space while he is in the process of working on them (home videos, etc. take up a lot of space while you work on them, at least his do). Once he completes what he's working on, he puts them onto a different internal SATA HDD..
i know that other folders (or libraries) can be moved/mapped elsewhere (I have done that myself), and I have no real need to re-map the desktop to a different drive, but he was just inquiring.. I dont personally think its a good idea to try it because if something goes wrong, you could screw lots of stuff up with your account, but I figured I would throw it out there..