In addition to what Patio mentioned, you can also just look up the model of the computer (if it's something like an Acer or HP or the like) or opening the side panel and reading the model numbers on the parts themselves, then downloading the driver from the manufacturer's website.
If the computer can't connect to the internet (network doesn't work without drivers for example) you can download the drivers from any other computer and copy them to a CD or flash drive.