A database used by the Windows operating system (Windows 95 and NT ) to store configuration information.
The Registry consists of the following major sections:

HKEY_Classes_Root - file associations and OLE information.
HKEY_Current_User - all preferences set for current user.
HKEY_User - all the current user information for each user of the system.
HKEY_Local_Machine - settings for hardware, operating system, and installed applications.
HKEY_Current_Configuration - settings for the display and printers.
HKEY_Dyn_Data - performance data.

Most Windows applications write data to the Registry, at least during installation. You can edit the Registry directly by using the Registry Editor (regedit.exe) provided with the operating system.  However, you must take great care because errors in the Registry could disable your computer.