Go to Dell Support and check out the network drivers for your computer model.

http://support.dell.com/support/downloads/driverslist.aspx?c=us&l=en&s=gen&os=WLH&osl=en&catid=&impid=&SystemID=DIM_PNT_P4_CEL_2400

Edit: There was something weird going on with the drivers download page--I had to refresh a couple of times to get the network, video and some of the other categories to show up!

afletche,

I think this is what you're looking for.

How to Install Drivers in Microsoft® Windows® on Dell Systems

Since the operating system was re-installed did you remember to go to drivers and downloads, enter your service tag(DO NOT POST SERVICE TAG here or your post will get deleted, since it contains your personal information), and install these drivers in this order.

Desktop System Software or Notebook System Software
Chipset or SMBus driver
Processor Driver (if applicable)
Video
Audio (sound)
Input Drivers (keyboard/mouse)
Modem
Network Card

Rick

I have reinstalled all drivers, in order, from the resource CD. When I go to install Broadcom 4401 Integrated NIC it comes up with instructions to reinstall the NIC driver by going to the Device Manager and finding Network Adapters, but that is not on the list. There is a yellow exclamation mark by ethernet controllers.

I am almost sure that the last time the problem did not involve a driver, and was somehing that took about 2 seconds to fix, but I could be wrong.

afletche,

The one that has the yellow exclaimination mark, uninstall it, then try restarting your computer and see if Windows Finds it, again.

Rick