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8/6/2003
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Fred Langa
Fred Langa
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The Explorer: Save Your Butt With DOS: Part 2

Make a custom boot disk -- while you still can!

Microsoft doesn't want you making bootable floppies anymore. In both the soon-to-be-released Windows Millennium Edition (the follow-on to Windows 98 that's due to go on sale in September) and in the current version of Windows 2000, none of the three traditional ways of making a bootable floppy work: The Windows Explorer diskette formatting function has no option to "copy system files;" the manual "Format" command doesn't support the "/sys" switch; and the manual "Sys" command only works on hard drives. So, Windows 98SE may be the last version of Windows in which you can easily make bootable DOS floppies. Clearly, Microsoft thinks that as we move forward we should do without low-level control over your PC, and that we shouldn't have the ability to access your files and hardware outside of Windows. I feel otherwise, and strongly believe that that low-level access can be a lifesaver when things go badly wrong. In fact, Part One of this series of "Explorer" columns explained why having easy access to a bootable DOS floppy can be a good thing for any version of Windows. But make no mistake: Microsoft is inexorably moving to the day when all versions of Windows are DOS-free. Despite its ongoing utility as a low-level diagnostic and repair tool, DOS's days are numbered. This series of columns is about ensuring that you have that desirable low-level control by helping you create a custom, practical DOS toolkit you can store in a safe place against future need -- even if you eventually end up using a DOS-free version of Windows. Part One offered you a plethora of DOS-related links to get you started. In this installment, Part Two, we'll update and expand on a DOS-related subject we last covered a year ago in "A Bevy Of Boot Disks" to create a custom boot or "emergency" disk you can use to diagnose and correct serious problems that may keep your PC from starting normally.

DOS Boot
A "boot disk" is any floppy disk that contains all the essential files to start or "boot" your PC minimally (in DOS) without using any files on the hard drive at all. Because it's self-contained, a boot disk lets you start your PC even if the hard drive is totally dead or inaccessible. (If you're not sure about how a boot disk works or are otherwise hazy on the concepts, check out "By The Bootstraps." That article can also show you how to optimize your Autoexec and Config files to gain an extra 10 percent "low" DOS memory, for free!) You may think you already have a factory-provided boot disk: When you buy Windows 98 SE, for example, you'll find something called the "Windows 98 Second Edition Boot Disk" inside the box, along with the CD. The boot disk typically contains the following factory-installed files:

Aspi2dos.sys
Aspi4dos.sys
Aspi8dos.sys
Aspi8u2.sys
Aspicd.sys
Autoexec.bat
Btcdrom.sys
Btdosm.sys
Command.com
Config.sys
Ebd.cab
Extract.exe
Fdisk.exe
Findcd.exe
Flashpt.sys
Himem.sys
Io.sys
Mscdex.exe
Msdos.sys
Oakcdrom.sys

But although the label says "boot disk," it's actually an install disk: It's optimized for the purpose of installing the OS from the CD to your hard disk. It's not optimal for trying to repair an install of Windows that's gone bad or that you want to alter. (Other versions of Windows have different but conceptually similar install disks.)

The "StartUp" Disk
A slightly different boot disk is the one that Windows 9x/ME creates during install or that you can create from Control Panel's "StartUp Disk" tab. In Win98SE, it typically contains these files:

Aspi2dos.sys
Aspi4dos.sys
Aspi8dos.sys
Aspi8u2.sys
Aspicd.sys
Autoexec.bat
Btcdrom.sys
Btdosm.sys
Command.com
Config.sys
Drvspace.bin
Ebd.cab
Ebd.sys
Extract.exe
Fdisk.exe
Findramd.exe
Flashpt.sys
Himem.sys
Io.sys
Msdos.sys
Oakcdrom.sys
Ramdrive.sys
Readme.txt
Setramd.bat

(Again, other versions of Windows 9x use different, but conceptually similar, files.) Although this is a true, bootable diskette with useful files, Microsoft doesn't really intend it to be used for general troubleshooting and repair. Instead, as explained on the Readme file on the disk, its primarily use is for simple troubleshooting and (as with the "Windows 98 Second Edition Boot Disk" previously described) as a means to install or reinstall Windows from the original CD.

Plus, the disk is very generic: Many of the files (the ASPI drivers, for example) are on the disk so it can recognize a wide variety of drive types. But your PC doesn't have a wide variety of drive types -- it probably has only one or two types -- so most of those generic drivers just waste space on the floppy. In fact, they waste so much space that Microsoft had to get tricky to fit everything on one disk: The floppy stores many of its most useful files in a compressed format within EBD.CAB ("Emergency Boot Disk.Cabinet"): When it runs, the floppy creates a RAM disk on your PC, decompresses the tools in the CAB, and copies them to the RAM disk. This works, but is far more complex than it has to be and can cause drive-letter confusion (the RAM disk will occupy a drive letter you may normally associate with, say, a CD). Plus, because the tools are stored inside a CAB, there's no easy way for you to add or remove tools specific to your needs. As a generic tool, this "Start Up" boot disk is OK and worth having. But there's an even better approach, and that's to create your own boot floppy that contains exactly (and only) the tools you need for your PC, in a simple, easy-to-use, no-smoke, no-mirrors, no RAMdisk form.

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