Short for Emergency Repair Disk, a Windows backup disk created by using the Backup utility. The ERD contains information about the current Windows system settings and can be used to rebuild the system if the file system becomes corrupt or the operating system will not start up. Whenever the Registry is altered – such as adding new software or hardware, installing a service pack or hot fix, making system modifications or adding new users to an account database – a new ERD should ideally be created to return the user to the most recent setup in case the ERD is needed to repair the damaged system. The disk can also be used to restore an old account that has been deleted if there is a copy of the system on an ERD from before the time the account was deleted.
It is important to note that the ERD is not a bootable disk.
This feature of Windows does not back up files or programs and should not be used as a replacement for regularly backing up your system.