Registry: HKEY_CURRENT_USER

HKEY_CURRENT_USER (HKCU) manages settings for the currently logged-in user.

Technically, 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-…).

On Windows NT systems, the settings for each user are stored in the files %USERPROFILE%\NTUSER.DAT and USRCLASS.DAT.

Apparently, processes running under the SYSTEM account (such as SearchFilterHost.exe) cannot access HKEY_CURRENT_USER for logged on users.