2 installs of XP Pro sp2 - one fine, one problematic

[hifiaudio2]

I have an MSDN subscription and downloaded the full version of XP Pro SP2. I have installed it on 2 computers. My main compuater, a Dell 840, is working flawlessly, no problems at all. However, my older computer, a custom built one, (ECS k7vta3 rev. 2 with Athlon xp 1600+, 256mb ram, geforce2 gts, western digital HD, and 3com nic that has the 3des encryption onboard) will not connect to the internet correctly. Both are going through my router, netgear wgr614 v4, and it has been set up properly. The older computer will connect to the internet for about 15 seconds, then just stops connecting. So I can start the web browser, put in any page - it will go there, download about half the page (and these are new pages, not something in the cache) and then just stop responding. I have turned off all firewall settings in xp, including going into the services tool under administration and setting the firewall to manual, instead of automatic, so it cant start without specific intervention from me. Anyone seen this before?