If you have a machine with no current operating system on it that will not boot from a CD-ROM, you must use this method. Setup disks are a set of four disks that form a minimal installation of Windows 2000
I wasn't aware there were CD-ROMs that you couldn't boot from.
Booting from CD wasn’t a feature for at least a couple years after the drives because common. Usually you’d use a boot floppy that had drivers for the CD drive.
Windows 95 (by default) wasn't CD bootable, you HAD to use a boot disk before you could use a CD for the rest. I think right after 95 came out the standard came out for CD booting. But before that OEM would make bootable CDs for their recovery media for 95.
I think at least some editions of Windows 98 couldn't boot from the CD-ROM either but had a boot floppy with the drivers. I hit this problem recently when trying to set up a Windows 98 machine.
I may be wrong but I think it'd be the same issue in that the bios wouldn't boot the OS from that sort of drive. For whatever reason that caused it I think it'd be a similar issue. That said by the time DVD drives being common enough for a server drive, most BIOSs would be able to handle it fine and a fair bit of time after this was needed.
Though I kinda thought with proper configuration cd rom drives were all bootable, but I wasn't working with servers in that era either so there were probably some mobos/bios that didn't work properly for booting a cd/DVD drive. Closest to the time I was familiar with was XP and pretty sure that was expected to be CD bootable in 2001. So maybe this kicked in the bios support for bootable non floppy disc drives?
I think early CD-ROM drives with proprietary interfaces were basically never bootable unless there were controller cards with option ROMs and I've never seen one.
These drives were from the early 90s, so that wouldn't have been the reason why Windows 2000 could use a boot floppy - maybe some computers had SCSI drives connected to controllers that only supported booting from hard drives
El Torito is an extension designed to allow booting a computer from a CD-ROM. It was announced in November 1994 and first issued in January 1995 as a joint proposal by IBM and BIOS manufacturer Phoenix Technologies. According to legend, the El Torito CD/DVD extension to ISO 9660 got its name because its design originated in an El Torito restaurant in Irvine, California.
A 32-bit PC BIOS will search for boot code on an ISO 9660 CD-ROM. The standard allows for booting in two different modes. Either in hard disk emulation when the boot information can be accessed directly from the CD media, or in floppy emulation mode where the boot information is stored in an image file of a floppy disk, which is loaded from the CD and then behaves as a virtual floppy disk. This is useful for computers that were designed to boot only from a floppy drive. For modern computers the "no emulation" mode is generally the more reliable method.
I vaguely remember fighting with getting burned OS install discs to reliably boot. Another fun thing from around that time is if you happened to plug in the floppy drive cable backwards any disks inserted would be erased. That's a great way to accidentally nuke your boot disk and be screwed if you weren't near another working machine with a floppy drive. Lots of little headaches like that really drilled in the concept of redundancies and lots of backups (as well as not mindlessly installing a floppy drive).
Back in the day, you needed a floppy drive to boot from a CD ROM (or a special reboot command). It wasn’t until a new BIOS firmware came out that allowed you to boot from CD ROM.
I bought Windows 95 on floppy disks when it first came out. I think it was 13 disks.
Microsoft used a special format for these floppies, called Distribution Media Format (DMF). It allowed them to fit 1.68MB onto each disk instead of the standard 1.44MB. I just went looking for information about that and found a web page that has not been changed since 1997:
