Whenever you have a piece of hardware - a mouse, keyboard, digital
camera or scanner for example - you need a piece of software in your PC
to make it function.
This software is known as a driver. A mouse and keyboard do need drivers
to function, but virtually every computer you use will already have a
driver installed. Sometimes the driver software does not load properly
when you start your PC, and a message like "Driver failed during
start-up" will appear.