ERUNT (Emergency Recovery Utility NT) is a small, portable utility for backing up and restoring the entire registry for Windows NT/2000/2003 and XP.
ERUNT allows you to back up the registry to a folder of your choice and it puts a copy of its restoration executable in this folder so you can burn that to a CD or copy to an external drive. ERUNT can be run from within Windows, DOS, the Windows Recovery Console or from a BartPE enviroment like UBCD4Win.
Why not just use the Regedit export registry option? Because it does not make a complete backup of the 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.
It is also possible to set up ERUNT to automatically make backups of the registry at a chosen interval. This is definitely a tool that every technician should have.
Download from Official Site – 772kb for installer version, 501kb for portable zip version.