HKEY_CURRENT_USER (HKCU) manages settings for the currently logged-in user. HKCU is a symbolic link to the subkey HKEY_USERS\{SID} where {SID} is the User's account SID (and starts with S-1-5-21-…). %USERPROFILE%\NTUSER.DAT and USRCLASS.DAT. SearchFilterHost.exe) cannot access HKEY_CURRENT_USER for logged on users.