User.dat is used for user specific information, which was previously held in the WIN.INI file.
System.dat is used for hardware configuration information and was previously held in the SYSTEM.INI file
The 6 Registry sub-trees may be edited through the regedit.exe program.
HKEY_CLASSES_ROOT contains information about OLE servers and file associations. It contains the same information that is typically stored in the reg.dat in Windows 3.x.
HKEY_CURRENT_USER contains the preferences of the user who is currently logged in. Receives stored information from the user's subtree located in HKEY_USERS.
HKEY_LOCAL_MACHINE contains hardware information and settings for any device installed in the computer.
HKEY_USERS contains preferences for every user that has ever logged into the computer.
HKEY_CURRENT_CONFIG contains settings for all hardware devices currently installed in the computer. Does not contain settings for devices included in HKEY_DYN_DATA.
HKEY_DYN_DATA contains dynamically stored data on performance monitoring.
Of the 6 trees shown here know the Local Machine and User Keys as a bare minimum.
The preferred method for updating the Registry is through the Control Panel or Device Manager. However, the Registry can be updated directly using the Registry Editor Utility (regedit.exe). Start --> Run --> regedit (opens the registry editor)
