WinXP network connection Tough one!

[monkey1340]

Firstly my system. P4 2.4ghz 800fsb, ecs 648mobo, Geforce 4 vid card, 40gb hard drive.
My problem seems simple but it has me stumped. I install windows XP for the first time, fresh install. Install all the nessecary drivers. I plugged the network cable in to the computer (onboard NIC) and I get nothing. It says in network connection the the sis-900 network is there, and working properly, but it isn't getting anything from the net, its not pulling an IP. I plug another computer into the same line to the cable modem, full internet no problem, so that rules out the possibility of it not being on my end. Back the the first computer, since the onboard card isn't working I plug in a 3com network card into a PCI slot. Start winXP and it detects the card, so I restart once the appropriate driver are loaded for the 3com, and when windows comes back up after restart the network connection is gone, the card is no longer dectected by my computer. So I decide to throw in another network card (now there are 2 card and one onbaord NIC) again it detects it, and it shows up as network connection 3, eventhough number 1 doesn't work, number 2 has just vanished. As soon as I restart the second PCI card has vanished in network connections. So for some reason my network connections are being hidden or taken out or not being read, I don't know what to do. Full format has been done since and I've reproduced the problem, anyone have any ideas. Could the w32.blaster.worm have anything to do with it.
Jeremy Any help would be greatly appreciated

[Telexen]

The worm could...if you have a network card try installing it seeing what it gives you.

[monkey1340]

Do you mean try installing the virus? I can't get the virus if I can't get on the internet
I don't think blaster has anything to do with it, a copmuter that has never been connectd to the net shouldn't be able to get the virus

[Telexen]

No try installing a seperate network card.

[monkey1340]

I've installed two 3com Network cards, they are just PCI cards I've put in, and they work until I restart then they vanish out of network connections and cannot be detected when i go add net ardware