This is the software publisher’s description.
Unlike Windows 98 or Me, within Windows XP or 2000 the Registry is never backed up automatically, and in XP it is backed up only as part of the resource hogging System Restore program which cannot even be used for a "restore" should a corrupted Registry prevent Windows from booting.
When Windows XP became pre-installed on many new home user PCs and, I decided to write a program which offers the ease-of-use of Windows 9x/Me ERU by Microsoft (hence the name ERUNT) to backup the Registry, as well as providing an auto-backup capability, for example at Windows start-up.
Or, before installing a new program for testing purposes one could save the Registry with ERUNT, install and test the program, uninstall it and restore the Registry to be 100% sure that no debris is left. Another option is to backup your Registry before you attempt a cleanse or optimisation.
