A nice alternative to system restore and works in nt and 2000 too
http://www.larshederer.homepage.t-online.de/erunt/
And it is different from exporting registry
http://www.larshederer.homepage.t-online.de/erunt/
On any Windows based computer there are several key files which together are called the registry. In them are found the instructions for how Windows boots, all of your hardware and network settings, what happens when you click on any item found within any program, and your security settings. The sum of these files is usually over twenty million characters which, if printed, would result in a phone book over four feet thick! Spyware, Trojans, and viruses all add entries to the registry which is how they become active on your system. Installing new software or hardware does the same. And, as you toodle along, almost every update or change modifies the registry.
Statistically, you are far more likely to have a problem with the registry than with any other part of your computer; so, having a backup is just about the most important thing you can do to prevent problems or undo them when they occur.
Microsoft knows the importance of having a registry backup and it is the driving reason behind System Restore; but, their restore points are too problematical and often fail.
Luckily, Lars Hederer has written a free utility named ERUNT which not only backs up the registry; but further allows many options for restoring the backups it creates. His website can be found here
You can choose to simply Open it when prompted which will start the installation or download it to the folder of your choice and double-click to install. When prompted about adding the item to Startup, I heartlly suggest you say yes.
Once installed, ERUNT will create a backup of your registry in C:\Windows ( or WINNT )\ERDNT\<today's date> each time the system boots.
If you want to try a hardware upgrade, attempt to solve a software problem, or have an extra backup before trying new software; you can easily do this by adding descriptive text to the end of the folder name if you run it manually. I, for example, have a folder named "01-31-05-b4-adaware" which I created before installing the new version of Ad-Aware.
Now that your registry is being backed up (and hopefully created manually when you want to experiment), what needs to be done if something goes sour?
The answer is surprisingly simple. Navigate to the desired folder and you will find an icon named ERDNT. Double-click and the program will walk you right through, including the necessary reboot to start running that backup.
So, if you should get infected with a nasty Trojan, want to completely undo the changes made by a new program, or undo almost any mistake, all that is needed is to go to a backup created before the problem and run the restore utility.
Bear in mind that this does not back up the files which may have been erased or replaced so it is not completely foolproof; but, is an incredibly useful tool for troubleshooting and can save you untold hours of grief when problems arise.
And it is different from exporting registry
The "Export registry" function in Regedit is USELESS (!) for
making a complete backup of the registry. Neither does it export the
whole registry (for example, no information from the "SECURITY" hive
is saved), nor can the exported file be used later to replace the
current registry with the old one. Instead, if you re-import the file,
it is merged with the current registry without deleting anything that
has been added since the export, leaving you with an absolute mess of
old and new entries.