In shortly this system let you rent out your HDD, and receive altcoin called Storjcoin X. It is not very smart to do something with this system, because you do not know who will use your HDD ( computer safety from viruses ) and Starjcoin X altcoin is not very popular - it is 33th place in a whole altcoin market -
https://coinmarketcap.com/assets/storjcoin-x/. How can you change Starjcoin X to Bitcoin, it is not included in instant exchangers.