login problem quastion

[dorino11]

hi.
need some help please

my imac stack on this screen:
http://www.up2me.co.il/v.php?file=42813518.png

didn't know where to find my main user or what can be this name and password
i think its something with
keychain or filevault

some idea? :/

 

[Audit13]

Is this a used computer you bought? If you cannot find the log in password, you could try erasing the hard drive and reinstalling the operating system.