During the life of a PC there are a load of drivers that are installed/uninstalled automatically for all the devices and peripherals you have, and you usually forget to uninstall them when you've finished using the device. That means they accumulate in your hard drive, becoming useless and unnecessary.
To end this problem, just run Driver Cleaner Pro. It deletes all the drivers you don't use in your PC. It is especially useful for drivers from ATI, Creative, nVidia, Realtek, SIS, 3Dfx, S3, etc. It also lets you view all the drivers in your PC and gives you information on each one.
Driver Cleaner Pro lets you, as a security measure, make a backup of the Registry, just in case something is deleted you didn't want to be deleted, and you then need that backup to restore the information like before.