Embeded LAN not talking

The other morning I discovered I couldn't connect to the WWW via my DSL modem. I first tried to browse into the modem to verify that it was "up ". Couldn't connect. I then attached a spare DSL modem and couldn't connect with it as well. Pressumed the Embeded NIC was bad. Windows XP SP3 says it's functioning normally. I popped in a 3Com PCI NIC and while Windows saw the new hardware I couldn't manage it either. Later hooked laptop to DSL modem and it works. Looks like the embeded NIC must be bad but why does Windows recognize it and the 2nd card and can't manage either one?
Any thoughts or past experience like this?

 

Steve, I took care of that early on. Reloaded both the 3Com driver and the VIA driver for the embedded NIC, no change. Was just reading about the OSI model of the 7 layers of TCP/IP protocol. It would seem that the physical layer is intact, hence the NICs are recognized as present and working but there must be a break in one of the data layers that control communication. Luckily I found an identical Mobo to replace and salvage my memory, cpu, etc. (My Board was only 2 years old) I've never lost one to this type of failure.