Create a Boot Floppy

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Addendum: since this article was written, all OS installation disc are bootable in their own right. Also consider using a bootable USB drive now that this BIOS option is iniversally standard. It can be sometimes be useful to create a boot floppy when working on older machinery or to use the floppy as the basis of a bootable CD/DVD.

I recommend you read The Right Order section before continuing

What do you do if your hard disk isn't or your Operating System doesn't? Answer: Thank God (or in this case, Andy) that you've got that boot disk...

3.5" ain't so small...
So you thought that was the last you'd be seeing of our friend, the trusty floppy eh? Think again. Technology and space requirements might have come a long way since the introduction of the floppy disk drive, but we still don't yet have a universal replacement which allows you to boot your system when all else fails.

So what do we mean by the term 'boot disk'? Well when you turn on your computer, the first part you see on-screen is the POST (Power On Self Test) where the BIOS tells the system what hardware is installed and how it's configured. Yep, your PC does this EVERY time it's turned on. Just in case something's changed. Stupid really.

After the POST, the system will look for an Operating System to use. Without an OS you can't use your computer, so there'd better be one somewhere and this is what makes the machine 'boot'. These days most machines can be configured to boot to one or more of a number of devices (both IDE and SCSI) including the floppy drive, the hard drive, the CD-ROM drive, the network card or even a Zip or similar high capacity removable drive. The boot selection order of these devices is configured in the machine's BIOS.

So why do I need a boot floppy?
I'm glad you asked. If you need to put a new hard disk in your PC, how do you run the software to prepare the disk when the hard disk itself is totally blank? What happens when your Windows system files become corrupt and your hard disk refuses to boot? How can you safely scan your hard drive for boot viruses? How can you connect your PC to a network server in order to download a disk image with which to configure your hard drive? All these and many more, are compelling reasons for having a boot floppy disk handy. Convinced? Then read on and get to love your 3.5".

Hector the sector
Most removable and hard disks contain special files which allow the system to boot. These might be thought of as a minimal operating system which allows you to perform certain basic tasks. The system will look for these files on a certain part of the disk, known as the Boot Sector.

When you view these files on disk, you can't really see which part of the disk they're physically located on. Suffice to say that the boot files must be in the boot sector of the disk and there's a particular way of achieving this, otherwise no boot, viz:

OPERATING SYSTEM CANNOT BE FOUND
UNABLE TO LOCATE OPERATING SYSTEM
WHERE THE HELL IS THE OPERATING SYSTEM etc..

And that's not all. Disks can be divided into usable chunks or Partitions, perhaps making one disk look like many. The boot files must be in the boot sector of the one (and only) partition which is marked as 'Active', otherwise no boot, like:

UNABLE TO FIND ACTIVE PARTITION
NOT GOING TO PLAY...you get the picture

See the Partition Theory menu for more details.

Get on with it p-leaze
Head getting full? Don't worry. For the purposes of your boot disk, you don't have to worry about partitions. Floppies have only one partition and it's usually seen as A: But they do have a boot sector.

So how do we get the boot files on the floppy? Well for the purposes of Microsoft based operating systems we have to 'Sys' the floppy disk. The first two files we're speaking of are io.sys and msdos.sys and you can't just drag and drop 'em onto the floppy 'cos they won't go into the boot sector. We use a utility called sys.com from the Windows\command directory.

Sys-ing a disk puts both of these files into the boot sector, where the system can find them on boot-up. A third file, command.com is usually also needed and could actually be dragged and dropped as it doesn't need the BS. However one wouldn't do this in practice as a sys from windows or DOS will put this file on the destination disk too. In fact command.com is DOS (and hence Windows) in its most basic form. Shock, horror, y'don't say...

Sys-ing the disk in DOS
Although not compulsory, I prefer to format a boot floppy to make sure it's free of bad sectors.
In DOS type:

C:\>FORMAT A: /S

- the /S switch copies the system files after the disk format. To copy the system files without the format, type:

C:\>SYS A:

Sys-ing the disk in WINDOWS

Note multiple partitions in Windows Explorer

Insert floppy disk. In Windows Explorer:

Right-click A: drive

Select FORMAT from menu

Under FORMAT TYPE, select FULL for full format with summary of possible bad sectors

COPY SYSTEM FILES ONLY does not format or erase files, but adds boot files

COPY SYSTEM FILES will add boot files following a format

Your disk should now have the three necessary files to make it bootable:

io.sys
msdos.sys
command.com

Delete drvspace.bin if it turns up - you don't need this.

What else do I need?
CD/DVD-ROM drivers may be required. Note also that most install CDs are bootable in their own right these days.

To use the boot floppy for hard disk preparation, copy the following files from the windows\command folder to the floppy disk:

fdisk.exe
format.com

Other useful files might include:

edit.com
scandisk.exe (also copy scandisk.ini)