There are several types of bootable CDs. For example: 1. DOS bootable CD. 2. Windows XP bootable CD. 3. Linux bootable CD. 4. Windows Live bootable CD. 5. Live Antivirus bootable CD. It is also recommended that every operating system installer CDE be bootable. Copying all the data from an operating system CD (e.g. Windows 98, Windows XP) to a computer and burning it to another CD is not bootable but it can be burned from a CD burner software (eg Nero) to CD to CD or by creating an ISO image. If it is bootable, why ? Each bootable CD has two portions : the data stored on one CD and the other is its boot sector. The boot sector is the part of the CD that contains the data that the CD needs to be bootable. This is usually the case when data is copied from a CD. Only if an ISO image of a CD is created it is added to it. Also added when CD to CD is copied because when CD to CD is copied the program basically creates an ISO image of the CD .