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. HKEY_PERFORMANCE_DATA This key provides runtime information into performance data provided by either the NT kernel itself, or running system drivers, programs and services that provide performance data. This key is not stored in any hive and not displayed in the Registry Editor, but it is visible through the registry functions in the Windows API, or in a simplified view via the Performance tab of the Task Manager (only for a few performance data on the local system) or via more advanced control panels (such as the Performances Monitor or the Performances Analyzer which allows collecting and logging these data, including from remote systems). HKEY_DYN_DATA This key is used only on Windows 95, Windows 98 and Windows ME. It contains information about hardware devices, including Plug and Play and network performance statistics. The information in this hive is also not stored on the hard drive. The Plug and Play information is gathered and configured at startup and is stored in memory. Hives Even though the registry presents itself as an integrated hierarchical database, branches of the registry are actually stored in a number of disk files called hives. (The word hive constitutes an in-joke.) Some hives are volatile and are not stored on disk at all. An example of this is the hive of the branch starting at HKLM\HARDWARE. This hive records information about system hardware and is created each time the system boots and performs hardware detection. Individual settings for users on a system are stored in a hive (disk file) per user. During user login, the system loads the user hive under the HKEY_USERS key and sets the HKCU (HKEY_CURRENT_USER) symbolic reference to point to the current user. This allows applications to store/retrieve settings for the current user implicitly under the HKCU key. Not all hives are loaded at any one time. At boot time, only a minimal set of hives are loaded, and after that, hives are loaded as the operating system initializes and as users log in or whenever a hive is explicitly loaded by an application. File locations The registry is physically stored in several files, which are generally obfuscated from the user-mode APIs used