i am trying to use my computer as gateway to internet to my another machine
the problem: operating system is fedora 4.

suppose the machine which have internet connection have two ethernet card.

1. 3com which have ip address of 192.168.0.2 is connect to my lan
2. dlink wireless card which is connect to router. The router is connect to internet via dhcp server.

I need to connect my 2nd machine which have ip address of 192.168.0.3 my server which local ip is 192.168.0.2.

But when i activate my eth0 which have ip address 192.168.0.2. my wireless pci card is stop browsing but it have connected to my router. When i refresh my wireless card with command. service NetworkManager start & NetworkMangerInfo then my eth0 is stop working.

I am new to fedora 4 or on linux platform.

It could be a routing problem, because when you activate the lan interface it should not take its network as default route.
you can check with netstat -rn when both are up, to see which one has the default gateway.

why will you want to use 2 network card to connect to one network there will obviously be conflict unless they are connecting to different networks or subnets
please explain what exactly you are trying to do
because if you have a router you dont need your system to be a gateway