These days neither floppy drives nor floppy diskettes are available which are used most of the times by PC users to create MS-DOS startup disks for Windows for troubleshooting or to flash their BIOS for update, these days they’ve been replaced by USB flash drives. Rufus is freeware portable tool lets you make DOS Bootable USB Drives easily and here is how.
Download and run the program executable which automatically detects USB flash drive if any plugged-in to your Computer and displays connected status with quick format and Create a DOS bootable disk pre-checked, all you need to do is click on Start button. After using the flash drive you need to format it in Windows to remove DOS bootable files created in it.
Rufus works on Windows XP/Vista/7.