I am using an online service.
I log in with a username X then log off. Fine!
I then uninstall the sofware service and try to delete all of its roots elsewhere in the registry too.
Later, I install it again, and oddly enough, my username still appears on the log on screen awaiting for password input. Is there any file left I miss deleting in the registry > or could it be that the service's server's database stored my username and IP ?
By the way, what portion of the installed components in my computer stored the signature of datetime, my identities to match against the server ?

Help me understand it please. thank you.