reload ethernet controller driver

Desktop 2005 Dell Dimension 5000. Support Tag U7670.  Running on Windows XP.   Problem:-   Operating system reinstalled recently using Dell CD. Coincided with changing ISP and adding a wireless gateway with the intention of my wife fitting a wireless adapter to her PC while my connection used the ethernet cable (faster, safer, more reliable?)  No BB!   Partial solution, fitted wireless adapter to my PC and went online via the wireless part of the gateway.  A big yellow ? against the ethernet controller in the devices manager list demonstrated that the driver had not been  loaded during the OS reinstallation.  Why  computer manufacturers include some, but not all, device drivers in their main reinstallation discs is a mystery.   The supplementary disc containing device drivers refused to reinstall the driver for the ethernet controller although I gleaned that it might have the code No. PCI\VEN_14E4&DEV_4401&SUBSYS_01991028&REV_01\4&10416D21&0&18F0.  If anyone here can tell this geriatric technophobe where to find and how to download and install the appropriate driver, I should be immensely grateful.