Most folks ignore that operating system installation procedure where it is asked if a boot disk (emergency disk) should be made.
While this boot disk is important in Windows operating systems, it is even more important in Linux, especially in a dual-boot system, where Windows and Linux exist together. Even if you boot using a bootloader existing on a system hard-drive, you should keep an up to date boot disk handy. If the standard boot process goes awry, toss the boot disk in, reboot, and then you can get in to repair the problem.