Network Cards

I have a Dell 8100 with a built in 3Com NIC and a Kingston NIC in a pci slot. The 3com is set for DHCP from the cable modem and the Kingston is set as a lan card 192.168.0.1 If I fire up the PC with both card enabled the 3Com will not connect to theinternet untill I disable the LAN card. After making connection the LAN card usally works OK. Any ideas??