The easiest way of updating your computer's drivers is letting a specified tool do it for you. One of the tools is Driver Pack Solution, there's a free and a paid version (for most users the free version will do everything they need).
Download it, let it scan your PC and install the right drivers.
All the manufacturers have made the drivers of their products available on their websites. All you need to do is to type your device's model number on the manufacturer's website and the latest version of the driver will appear. By downloading and installing the latest version of the driver in your computer, you will update the already existing driver.