Hi JimPhreak,
The easiest method of trying the downloaded drivers is to boot the Dell E7480 Computer into winpe and then plugin a USB-Stick with the download drivers.
In WinPE type drvload with the Path to your .inf File on your USB-Stick. After the Driver is loaded type ipconfig can check if you get an IP Address.
http://www.symantec.com/docs/HOWTO9542
To check the driveletter of your USB-Stick you can type diskpart -> list volume
After you have verified that the driver works you can add it to the Preboot environment and recreate it.
Network23