Tweaking.com - Registry Backup is a free backup tool that will use the Windows Volume Shadow Copy Service to backup your system registry.

Features:

The program is 100% free.

One click backup and restore.

Can restore from Windows Safe Mode.

Portable version can be ran from a thumb drive and keep backups of multiple systems.

Automatic cleanup of older backups.

Set and control scheduling options.

Can backup & restore all user profiles on the system, not just the ones that are currently loaded.

Control which registry files are backed up or restored.

Detailed logs are saved with each backup.

Multiple easy restore options.

Online videos showing how to use the program and how to use the different restore options.

Changelog:
v1.6.0
Windows vista, 7 and newer added a new registry hive to the system called Components. The program now supports this new registry hive.