If your computer develops a problem that keeps it from accessing your hard disk, you need some other way to boot your system. The answer is an emergency boot disk.
Macintosh systems come with either a bootable CD-ROM or a bootable floppy disk, as does Norton Utilities for Macintosh -- a must for all Mac owners. If you are using Win95/98/ME, you need to make an emergency boot disk, which you can make with the Add/Remove Programs control panel. Select the Startup Disk tab, and you're led through the process.
On Windows Vista and Windows 7/8, the original installation disk for the operating system acts as a boot disk for the computer system as well. The installation disk also includes Startup Repair and other tools on the System Recovery Options menu that you can use to attempt repairs or restore data from a backup. In Windows 7/8 OEM systems, you'll want to create the Recovery DVDs and a Startup CD. Without the Recovery DVDs, you won't have any software to load back onto a computer in case of a complete hard drive failure. The startup disk will allow you to attempt repairs and get to the data on the hard drive. An essential task if there is a problem with your hard drive.
On Windows XP, you can generally boot directly from the Windows XP CD-ROM, however in some cases you may still need a set of boot floppies. In this case, click one of the links below to download a program to create boot floppies for Windows XP Home or Windows XP Pro editions.
Under Windows 3.1, you have to create the disk yourself. Go to the DOS prompt and enter the following commands. Be sure to have a blank floppy handy.
FORMAT /S A:
COPY C:\AUTOEXEC.BAT A:
COPY C:\CONFIG.SYS A:
COPY C:\WINDOWS\SYSTEM.INI A:
COPY C:\WINDOWS\WIN.INI A:
Now, if you can't boot from your hard disk, you will have a way to get your system started so you can deal with the problem.
For other Windows Operating Systems, visit Bootdisk.com to download a boot disk creator for your version of Windows or DOS.