Prep to sell laptop

My granddaughter wants to sell her 2 year old Windows 7 laptop. I'm preparing it to sell. I've run the Recovery software to restore it to its original state. I want to use Eraser, as was recommended on another post on this site, on the unused portion of the hard drive, but the window that requests a user name and a computer name has come up. Should I type something in these blanks so I can run Eraser? Not sure what to do here.

Thanks
Peg