You can run multiple computers with a single keyboard and a mouse by using an amazing little app called Synergy. You simply load the app on the computer you want to use as the Server (the computer with the keyboard and mouse you want to use) and then load the app again on the computers you want to be controlled by your Server. The configuration is very simple and in minutes you are controlling two or more computers from your Server computer. The video below will go into configuring Synergy and how to use it.