Socket A PC with Network card AND Asus A8N sli PConboard LAN

My Socket A PC has no LAN but has a Network card.
My Asus A8N sli nforce4 PC has two onboard LANs.
They are connected with cat5 cable.
They both have winXPsp2
1. They network OK.
2. The Asus one can get on the BroadBand when Socket A PC has it installed.
BUT
3. Socket A PC does not connect on the Broadband when the Asus has the
BBand installed.

No 3 above is my prefered case.

Is there an expert who has an "A" socket PC with Network card, dialing the Broadband of a PC with onboard LAN, and both on winXPsp2 ?.

Only such a person need try to help PLEASE.

Thank you, nick