To clarify, I had thought that the disk which came with the unit had the same existing OS and that is why I attempted to reload the OS to clear out whatever was on the unit from the previous owner, it was only after trying to reload the OS on the disk that I saw the disk contained the older version. That is why I asked earlier if there's a back up of the existing OS anywhere on this unit so I could reformat and use the existing unit but if not and I will have to purchase a new OS then why not purchase the most most up to date OS which can work with this unit? Hope this clears up everything?