Windows registry is a centralized and hierarchal database present in Microsoft Windows operating system.

Windows registry is used to store configurations and settings for windows operating system.

Windows registry also keeps a record of all the programs and software that have been installed on your computer.

Windows registry also configures the operating system for users, hardware devices and applications. Windows registry also contains information about low level operating system components.

Windows registry replaced the old .INI file system that was primarily text based. 32 bit versions of windows contain all 32 bit registry keys however in 64 bit version of windows operating system the registry keys are divided into both 32 bit and 64 bit keys. 

Windows registry files can be accessed and modified by the user using the Microsoft registry editor program. The registry editor is free program that is available in all versions of registry based windows operating systems.

To access the registry editor go to start menu. Open the run command dialogue box. In the writing area of this dialogue box type regedit and press enter.

After this the registry editor application will start. Here you can add, modify or delete the registry entries of a software or hardware device.

The program functionality will change according to the value entered. However it is extremely important to create a backup of registry before editing it. Changes in the registry files may render some programs or software permanently non functional and may cause some programs to function improperly.