User Profile Hives
With the hive registry, each time a new user logs on, a new directory is created for that user with a separate file for the user registry. This is called the user profile hive. A user's hive contains specific registry information pertaining to that user's applications, desktop, environment, network connections, and printer settings. The user profile hive contains all data under the HKEY_CURRENT_USER key. When the current user is logged off and another user is logged on, the new user's hive is mounted, and the data under HKEY_CURRENT_USER changes.
The registry subkey ProfileDir under the HKEY_LOCAL_MACHINE\init\BootVars registry key indicates the location where all user directories are placed. Each directory is given the name of the user to whom it belongs.