Basically, they took off in the Windows line with NT server. The idea was to take your user specifics, preferences, user registry hive, that sort of thing, and dump them on the server so that you'd have access to your personal set of ugly window colors and ugly, unreadable fonts on titlebars and controls no matter which workstation you happened to be on. They are loaded at logon from the server since, what, Win98? Maybe earlier--can't remember back that far.