User-specific registry entries.
From MS:
"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."
HTH