A startup disk or boot disk is a miniature operating system (OS) on removable media, such as a CD, memory stick or floppy, that can be used to boot a computer, bypassing the installed operating system when one is present. Though a startup disk is more commonly placed on a disc (CD) rather than a disk (floppy), the original spelling continues to be used as a carry-over from when floppy disks were the only type of boot disks available.
There are many situations in which a startup disk comes in handy, and others in which it essential. The most important use is for recovery from a non-bootable system crash.
If a computer won’t boot due to a problem with the installed operating system, a boot disk created by the operating system can be used to repair a damaged system. It will replace system files with fresh copies, hopefully making it bootable again.
An OS-created boot disk might also be used to reinstall the operating system from a drive image located in a hidden partition at the beginning of the installed drive. Newer systems use this method rather than supplying users with the OS on a disc. The drawback of this method of recovery is that the system is returned to the state it was when first purchased, losing all changes including user-installed programs and data.
A far better method is to use a startup disk designed to replace the existing image with a current backup image made prior to the problematic date. This eliminates the need to troubleshoot the problem, if that avenue is even available, and will retain all programs and data as of the last backup. Some backup programs like the free Macrium Reflect©, supply the user with a link to a file that can be downloaded and burned to disc to create a custom startup disk with the Macrium Reflect© backup program preinstalled. This disaster recovery disc takes all the worry out of a fatal crash, providing one makes regular backups, preferably to an external drive.
If restoring an image won’t work due to mechanical hard drive failure, a startup or boot disk can be used to format and partition a fresh hard drive. While an OS disc will also do this some people prefer using specific tools from custom made boot disks.
Occasionally, it’s a good idea to run maintenance tools from outside the operating system, which can be done using a startup disk with the appropriate programs. Running a "check disk" routine will comb the hard drive looking for errors in file structure and formatting, optionally fixing problems along the way. This can prevent data loss and improve disk performance. Check disk can also be scheduled from within Windows® systems to run at the next boot, before the OS starts.
Anti-virus and anti-spyware scans are also better run from a startup disc, as files become locked and unavailable to the scanner when the OS is in use. Stealthy malware might also be able to hide inside OS processes when the boot drive is mounted and active. Using a boot disk, the entire drive is available for scanning.
There are several ways to create a startup disk. In the old days, certain DOS® files were copied to a floppy, but today, portable editions of OSs can run on a CD or memory stick, using only portable storage and RAM. This makes it very convenient as the boot disk can run in a familiar point-and-click environment.
For intrepid geeks, BartPE© Builder is a free, portable Windows® environment that can be customized with various tools and programs, and it includes network support. This allows one to troubleshoot a problem by accessing the Internet from the startup disk. Various tutors are available on YouTube® for the creation of a customized BartPE© boot disk. Linux® boot disks are also available, as are tools inside particular backup programs, like the previously mentioned Macrium Reflect©.
Operating systems also have tools for users to create a startup disk. These discs repair damage by replacing system files, or they might offer to return your system to the state it was when new; a last resort for most people. To learn more about how you can create a startup disk in your OS, consult the Help menu.