Using Nero Burning ROM you can create a bootable disc with which the computer can be started without having to access the hard drive. For this reason a bootable disc is often used as an "emergency disc" to start the computer if it is not possible to access the hard drive.
Bootable discs are created in accordance with the "El Torito" standard, an extension to the ISO-9660 standard which defines the structure of data discs. The disc contains a boot image and an ISO part. The boot image contains all files that are required to load the operating system and to start the computer. The ISO part can contain any number of data files that you can back up using this method.
To ensure that a computer can boot from disc, the start sequence must be set in the BIOS of the computer in such a way that the drive is addressed first as the boot drive (start sequence CD-ROM, C, A for instance). In the case of a SCSI CD-ROM drive, this must be connected to a SCSI adapter with a separate BIOS whose settings can be modified accordingly. (This will only work when there are no IDE hard drives present, as these precede the SCSI adapter in the boot sequence).
When booting from a disc, you can only start an operating system that does not write to the medium, such as "MS DOS" or "Linux". During booting Microsoft® Windows® 2000 and Microsoft® Windows® XP write to the medium from which they are being booted. This is not possible with a disc and so the process is canceled and the PC cannot be started.
Bootable Disc Template
For Nero Burning ROM, the template for creating a bootable disc can be either a logical drive (e.g. the C: drive) or a drive image file which contains the contents of a drive as a file sector for sector. If the template for the bootable disc is a logical drive, the bootable disc will emulate this when the system is booting. There are three emulation types:
Floppy emulation: This requires a bootable floppy disc for creating the bootable disc. At startup the bootable disc emulates a floppy disc in drive A:. In the process, the drive letters increment, so that Drive A: corresponds to the bootable disc. Floppy drive A: can be accessed as B: after booting. The volume of the start data is limited by the capacity of the floppy disk (e.g 1.44 MB).
Hard drive emulation: A bootable hard drive is required to create the bootable disc. At startup the disc emulates Drive C:. All drive letters from Drive C: increment by one. The volume of the start data is limited by the capacity of the CD (e.g. 700 MB) or DVD (8.5 GB). If, for instance, you have a 200 GB hard drive with only one (200 GB) partition, you cannot create a bootable disc from it without repartitioning your hard drive accordingly beforehand.
No emulation: In this process the drive names are not changed. This type is used for bootable installation CDs. This setting is intended for users who do not require a floppy or hard drive emulation and who want to install their own device driver.
Nero Burning ROM