Most people probably do not pay a lot of attention to the process called “booting” that goes on when they first turn on their computer. However, there may come a time when it is necessary to get involved in the boot process in order to remedy some problem and to make use of something called a boot disk (or as Microsoft sometimes calls it, a “startup” disk). You may go through life without ever having to use one, but like a spare tire for a car, a boot disk is something everyone should have. There are various versions of boot disk possible, but the basic contents are some form of operating system that will allow you to run your computer from somewhere other than the hard drive.

When you turn on your computer, it has to go through a whole series of steps before it ever gets around to loading your programs; it has to “pull itself up by its own bootstraps” (the origin of the term “boot”). Before the central processing unit (CPU) can access the keyboard, monitor, hard drive, or other basic components, the CPU has to get instructions from a small amount of permanently stored code called the BIOS (Basic Input/Output System). After the CPU has been instructed on how to get things in and out, the BIOS then tells the computer where to look for its next set of instructions. In most older machines the computer would first look in the A: drive and if nothing was there it would then look on the C: drive. (Just about everybody of a certain age has probably gotten one of those “Non-system Disk” messages when they forgot and left a diskette in the A: drive). Nowadays, the BIOS is usually set up so that the CD drive is included in the boot sequence. The sequence may be first the CD drive, then the A: drive, and finally the C: drive or may be some other permutation of the order of the drives, depending on your system. Thus there is an option to run the computer from somewhere other than the C: drive in case that becomes necessary or desirable.

An example of such a situation is when you sit down at your computer, turn it on, the BIOS does its thing and then nothing more happens. Or perhaps you get some messages on a black-and-white screen to the effect that Windows is on strike and will not load. What now? Assuming that you have previously done all the steps that are supposed to be part of routine maintenance, you may have a bad hard drive or perhaps a Registry that has gotten corrupted. If the hard drive is totally dead, a boot disk won't do much good until you get a new hard drive, but if the problem is something awry in Windows, then a boot disk may very well allow you to repair the problem. If you have a full bootable Windows XP installation disk, the Recovery Console is another way to deal with problems. Unfortunately, it is now pretty general practice for major vendors to provide only a recovery disk when you purchase a PC. Even if you do get an actual Windows XP installation disk, it is likely to be an OEM version and may lack the Recovery Console. Having an emergency boot disk can save you a lot of trouble.

Boot disks for Windows XP

The term "boot disk" can have several meanings. Personally, what I want is a disk that can read and write to the hard drive and that contains some functions that will help repair problems. This is not the type of disk described by the Microsoft literature. Their emphasis is on installing Windows XP rather than repairing it or on circumventing certain kinds of startup problems. This has given rise to some confusion in discussions that I see on the Web. There are at least four kinds of bootable disk described by Microsoft. To help sort things out, I list them below.

Startup disk (also called a boot disk by Microsoft)

This is the disk described in three Microsoft knowledge base articles given in the sidebar. The articles are quite similar and describe a disk whose purpose is to get Windows started if certain basic startup areas or files get corrupted. It consists of a blank diskette formatted in Windows XP (this formatting is essential, see last section below), to which have been added the system files NTLDR, ntdetect.com, and boot.ini. (also, bootsect.dos in dual-boot systems). These files must be added manually. There are no other functions on the disk and it is designed solely for the purpose of booting up the Windows operating system currently on your system. People sometimes confuse this disk with the version described next.

MS-DOS startup disk

This is a DOS diskette made by selecting the option "Create a MS-DOS startup disk" in the format dialog in a Windows XP system. The format dialog is reached by going to My Computer, right-clicking on the A: drive and choosing "Format..." This disk has certain DOS functions but cannot read disks formatted with NTFS. If a DOS disk is desired, a better choice might be the same one as is described for Windows 98. A DOS NTFS reader can also be added

Windows XP Setup boot disks

This is a set of six diskettes to be used in getting Windows installed when the system cannot use a bootable CD. Their only function is installing Windows. They are described by Microsoft here. Again, these are sometimes confused with one or the other of the two kinds of startup disks described above.

Bootable Windows XP full installation CD

If you are lucky enough to have one of these instead of a "restore" disk or abridged OEM version, you have access to the Recovery Console and many system tools.

Bootable CDs

The best type of boot disk for XP is probably one of the bootable CDs that come with a variety of diagnostic and repair tools. If you have a system with NTFS, you will want a way to read and, if possible, write files on the hard drive. Several references are given in the sidebar. You can either download the particular setup at one of these or read the instructions on creating your own CD.For example, Fred Langa gives detailed instructions on putting together the "perfect rescue tool". Fred also describes the details of the latest BartPE CD from Bart Lagerweij.

Complete Linux systems on a bootable CD

Another intriguing possibility is the Knoppix CD. This is actually an entire independent Linux system with much software, all on one CD. Because it can read NTFS, however, it can also help repair a sick Windows setup.(Writing to NTFS is trickier. See this reference.) Knoppix has a browser and you can go on the Web to download something you need for an ailing system. There are also other Linux distros such as Ubuntu that can be run on a single CD. Several references are given in the sidebar.

Booting Windows XP from a thumb drive

Provided that your BIOS recognizes booting from USB, you may be able to boot from one of those handy flash memory devices known by various names but often called a "thumb drive". There are some possible technical complications that may not allow every system to boot this way but for many systems it is possible to have Windows XP run from a thumb drive. Fred Langa has an article giving the details.

Boot disks for Windows 98

For those who continue to use Windows 98 and who still have an operating A: drive, detailed instructions on how to create a DOS boot diskette with useful functions are given on this page.

Boot disks for Windows Me

For whatever reason, Microsoft removed from Windows Me the ability to format a diskette with system files. A “startup” disk can still be prepared as in Windows 98 but obtaining a boot disk as described for Windows 98 is more roundabout. If you have access to a Windows 98 system, simply use a disk prepared in Windows 98. It works just fine for Windows Me. Ignore the message “Starting Windows 98” that you always get. You are starting DOS, not Windows of any kind when you use the boot disk. Some Windows Me systems may have the folder C:\Windows\command\ebd installed. In that case format a diskette and then copy the files io.sys and command.com to the diskette. Note that io.sys should be marked as a hidden file. The diskette will then be bootable but the list of files given on the Windows 98 page will still have to be added.

Watch out for differently formatted diskettes

If you have ever tried to use a diskette formatted in Windows 98/Me to boot into Windows 2000/XP, or vice versa, you will have encountered the fact that the boot sectors of a formatted diskette are not the same for all Windows systems. The boot code of a DOS/Win9x/ME diskette loads and executes the IO.SYS file whereas the boot process of Windows 2000/XP involves the NTLDR file. Many preformatted diskettes have DOS formatting and will not work as a XP startup disk unless reformatted in XP.

Boot disk for Windows Vista

Microsoft has a free download called Windows PE that allows you to make a bootable CD. Here is Microsoft's description:

Windows Preinstallation Environment (Windows PE) 2.0 is a minimal Win32 operating system with limited services, built on the Windows Vista kernel. It is used to prepare a computer for Windows installation, to copy disk images from a network file server, and to initiate Windows Setup.

It provides read/write access to NTFS filesystems, 32- and 64-bit hardware drivers, and network connectivity.