An emulator of the Microsoft Disk Operating System (MS-DOS) for Linux/X11. Enables Linux to run many DOS programs - including some DPMI applications. http://www.dosemu.org/
A bootable-disk emulator - it reads a diskette image file (a file that contains all the sectors of a floppy disk) and boots it. This way, you can boot (and run) a bootable diskette off of your hard drive. http://www.oldskool.org/pc/flopper/