<blockquote>For information about generic boot/recovery discs, see Recovery disc</blockquote>
A Microsoft WindowsEmergency Repair Disk (ERD) is a specially formatted bootable (for some Windows operating systems) media made by some Windows operating systems that contains information about a particular Windows installation, first seen in Windows NT 4.0. This disk can be used to restore a computer to a bootable state if the registry or other fundamental system components are damaged.
Windows 2000 uses what is called an Emergency Repair Disk but it is not bootable. Windows XP uses something very similar to the Windows 2000 Emergency Repair Disk, but it is called Automated System Recovery.