In simple terms the Windows Registry can be thought of as a file containing an extended inventory of all your PCs hardware and software.
When Windows starts up it consults the Registry in order to know how to relate to your specific hardware and software.
It's a file that's essential to Windows. If it gets corrupted Windows won't be able to function properly.
And it does get corrupted; rather too often actually. That's why it's good practice to have a backup copy.
Easy, you say, I'll just copy the file to another location.
In Windows 95, 98 you can do just this. The Registry consists of two files system.dat and user.dat located in the Windows folder and you can simply copy these to another folder to create your registry backup. ME adds a third file, classes.dat, but it too can be simply copied.
This simple approach won't work with Windows NT and later versions as the Registry files are locked by the system and can't be easily copied.
Windows addresses this by providing automatic backup of the Registry as part of the automatic System Restore feature. This feature is enabled by default when Windows is installed.
If you have left the System Restore feature enabled on your PC then your Registry is automatically being backed up. If it gets corrupted Windows will automatically try to recover it from previous restore points.
However, many users, me included, turn the System Restore feature off as it is a notorious disk space hog. Once turned off, your Registry is no longer being backed up.
Thankfully, there are a number of utilities that will back up your Registry. One of the best is also free. It called ERUNT.
ERUNT (Emergency Recovery Utility for NT) will backup the Registry for all Windows systems from NT onwards. It also allows you to recover from backup either through a special recovery program or through the Windows Recovery Console.
And it's fast, very fast.
With ERUNT it's also possible to set up automatic Registry backups using the Windows Scheduler.
As a bonus, ERUNT includes another utility NTREGOPT that allows you to defragment your Registry. To be frank, I've never myself seen any performance improvement from registry defragging but then again it does no harm either.
ERUNT is easy to use but it's not intended for raw beginners. Raw beginners will most likely have System Restore enabled anyway so they won't need to back up their Registry.
Freeware, Windows 95 and later, 773KB