The registry is a database in Windows that contains important information about system hardware, installed programs and settings, and profiles of each of the user accounts on your computer. Windows continually refers to the information in the registry.
Backing up the registry is a very good strategy for preparing for a disaster such as an infestation with malicious software (viruses, trojans, worms, rootkits).
The following steps will enable you to backup the registry:
In the event that something happened and you want to restore your registry, simply double-click on the backup reg file or go to File->Import in the registry window.
Note: The above steps will work for Windows XP, Vista and Windows 7.