Lets say you have a printer that someone gave you or a webcam that someone is no longer using but you could use it. The catch is that the person who gave it to you did not have the installation CD.

The files that get hardware to run are called drivers. These drivers can be found online. If you go to the manufacture of the hardware's website you will find a support tab. Click that and you should see a link to drivers. Choose the driver that matches the hardware device that you are using.

Follow up:

If this method does not work, go to Google and type in the model number, manufacturer, and the word "driver". For example, if you want to find a driver for a printer, search for something like "HP Deskjet 3000 driver" or "HP Deskjet 3000 driver download". The results should give you links to download the driver.

Now open up Device Manager. This can be done by going into the Control Panel (in classic view) and double clicking on Device Manager. This will show all of the hardware that is connected to the computer at the moment. Find the device that you want to install. It should have a yellow question mark over it if Windows did not identify the driver.

Right Click the device and install/update the driver. Go to the directory where the driver is located and install the driver. Windows will now assign that driver to the device and the yellow question mark should now be removed from Device Manager and the device should be working correctly.