$Driver 
A special piece of software that sits between Windows and a peripheral and translates the instructions from Windows into a form that the peripheral can understand. In DOS, before Windows 95 arrived, all drivers were loaded when the PC was first switched on from within the CONFIG.SYS file. A lot of drivers are built into Windows, although some will still have to be loaded from the CONFIG.SYS file, which is why your screen flashes between text and graphics mode when you first switch on your PC and it loads Windows 95. (See also CONFIG.SYS.)