The driver depends on the particular hardware, and can usually be found on your manufacturer's site if you search under Support for your model. Do you know the model?
Alternatively, a very clever member here posted directions on how to identify any hardware that needs a driver. See the second post here: http://www.tomshardware.com/forum/ [...] e-download , from Saga Lout.
Please satisfy my curiosity: how do you know that this is a driver issue?