HKEY_USERS, sometimes referred to as HKU, is one of many registry entries in the Windows registry.
What is Hkey_users?
It contains user-specific configuration information for all currently active users on the computer. This means the user who is currently logged in (you) and any other users who are also logged in but have since "switched" users.
Each registry key located under the HKEY_USERS hive corresponds to a user on the system and is named after that user's security ID, or SID. The registry keys and registry values located under each SID control settings specific to that user, such as mapped drives, installed printers, environment variables, desktop wallpaper, and more, and are loaded when the user first logs in.
Since it is a registry axe, you can easily find and open it via the Registry Editor:
