Overview#HKEY_CURRENT_USER (HKCC) stores settings that are specific to the currently logged-in user
HKEY_CURRENT_USER is a link to the subkey of HKEY_USERS that corresponds to the user; the same information is accessible in both locations. The specific subkey referenced is "(HKU)\(SID)\..." where (SID); if the "(HKCU)" key has the following suffix "(HKCU)\Software\Classes\..." then it corresponds to "(HKU)\(SID)_CLASSES\..." i.e. the suffix has the string "_CLASSES" is appended to the (SID).
On Windows Server NT systems, each user's settings are stored in their own files called NTUSER.DAT and USRCLASS.DAT inside their own Documents and Settings subfolder (or their own Users sub folder in Windows Vista and above). Settings in this hive follow users with a roaming profile from machine to machine.