Updating my arduino drivers

I have tried on both my windows 7 and 8 machines to install the arduino drivers when i plug in my rep rap. I find the unknown device and continue to try to update the driver. I navigate to the directory and click on the driver folder. The arduino.inf file is not there when i go there. If i look in this file through my file explorer it is there. How can i make this file show up when updating the driver??