Well, the simple case would be to create a shortcut to the command "command.com".
If you were to go to Start->run, you you type in "command" or "command.com" and run it, you get a MS-DOS prompt. BTW, win9x runs on top of something very similar to this.
So, right click on the desktop, and say new->shortcut... and put that in there, and you're set.