This caused Windows to create a temporary profile for the user’s logon session. A user profile consists of a directory, %UserProfile%, into which applications save user-specific configuration and data files, as well as a registry hive file stored in that directory, %UserProfile%\Ntuser.dat, that the Winlogon process loads when the user logs in. Applications store user settings in the registry hive by calling registry functions that refer to the HKEY_CURRENT_USER (HKCU) root key.