Hi. Update..........downloaded W10 to a USB stick and urrently trying to install a new W10 from a memory stick but there does not seem to be anything in the BIOS that directs the pc to install from the USB.  Therefore I'm installing from the 'set up.exe' on the memory stick   
I have taken possession of an Inspiron 27-7775 AIO from an other person. I installed a new SSD and successively turned it on to reach the Windows 10 front page. The previous owner Email/User name was displayed and a password was required to login to the PC. After going through the 'Lost Password'  process (with previous owner) a new password was entered and Windows 10 was operating, but all the previous owner's files owner's files were also displayed. I've not installed a new SSD/HDD on the 'newer' pc (Windows 10) and I'm unsure how to change the previous owner's details which are locked to the AIO PC, to my own login details. Hopefully, a simple answer is available. With thanks in advance from a new member of the community.
Inspiron 27-7775 AIO, Windows 10, change of ownership