This article is from the Mac communications FAQ, by Bruce L Grubb BruceG6069@aol.com with numerous contributions by others.
To change the owner and name of your Macintosh under System 7, select
"Controls Panels" from the Apple Menu and double-click on the
"Sharing Setup" Control Panel.
The Chooser "user" is the "Owner name:". Change it like any standard
edit field. The name of your Macintosh is the "Macintosh name:".
Also on this Control Panel is a button to turn File Sharing on and
off. When File Sharing is on, you cannot change the name of shared
disks. If you are trying to change the name of your hard disk but
cannot get the name to turn into an edit field, File Sharing is
probably on. Use the Sharing Setup Control Panel to turn File Sharing
off, change your hard disk name, and then turn File Sharing back on
(unless you have no need for it).