GET READY FOR THIS!!!!!!
Dell's integrated ethernet sucks so much, it took me 3 hours on the phone to dell to get it figured out, so when I re-installed XP yesterday/today, I just spent the extra 30 bucks for a nice PCI ethernet card, which worked BEAutifully. Yeah, I really suggest an add on card, because the integrated dell one, when I got it working finally, would crash my DSL after a few hours of playing online games, and this was a integrated ethernet related hardware problem.
If you do spend that extra $ on an add on card, don't install it until you have rebooted, and on the Dell Bios loading screen, quickly hit F2 and release before the Windows loading screen comes up, and go into the BIOS, and you will see options for integrated devices (mine was under the name Legacy something something), and go there, and turn it to off. Then hit escape, and "save and exit " then let it turn on, then turn it off, unplug all the cables (*ALL*) and pop in the new PCI card, turn on, and I'll bet you $50 that it will work.
You may also want to try getting on the internet with a Dial Up provider, and doing a windows update, and see if it gets a driver for the card/integrated ethernet, which may not be under the
"important" windows updates, but under the optional extra's.
BEST OF LUCK, YOU WILL NEED IT!!
Yan