--All Windows stores its configuration information in a database called the registry. The registry is the central storage for all computer configuration data.

--Although the registry appears to be in one file, it is actually placed on your computer in several files. Depending on your system configuration, registry files can be found in any of the following locations:

C:\Documents and Settings\User Name\ on Windows 2000, XP.

C:\Windows\System32\Config\ on Windows 2000, XP.

C:\Windows\ on Windows 95, 98, ME.

C:\Windows\Profiles\ on Windows 95, 98, ME.

--In windows NT, 2000 and XP not possible to back up registry files while the operating system is running. Registry files remain fully locked all the time while Windows is running, But here You can use an integrated Windows XP's System Restore feature for registry backup.

--But using registry editor (regedit.exe) you can to export partial or complete copies of the registry, while the Windows is up, and the exported files can then be backed up with any other traditional file backup utility. You can follow these simple steps to back up the whole registry or any particular registry subkey:

The exported registry file is about 10-50 MB in size on a typical Windows NT/2000/XP installation.