You have an offbeat setup and will have to create your own way of doing things.
http://support.microsoft.com/kb/q199346/ notes this issue and unless you have a second NIC, it won't share by design.
With a machine that does have a solid internet connection via satellite, wireless internet or "mystery" connections, it gets to run ICS (it's a common Windows acronym I leave to you to decipher) so it can share said connection on its NETWORK INTERFACE CARD or NIC.
The BEFSR81's WAN port would go to the ICS Host's NIC with the proper cable (you figure out if straight or crossover) and then you must sort out if the ICS is using some 192.168.1.1 type network which the BEFSR81 would have to use some other IP address scheme.
It can work, but you will become a mini-expert on your custom setup.
Hope this helps you create your new network,
PS. This may be my only reply on this thread since it's too sparse in information plus it's going to be a very custom setup. You need to become the expert too.
Heres my problem:
I have a WiFi isp that utilizes a pci card to interface the antenna.
I just bought a linksys dsl/cable router BEFSR81 wired router.
The installation cd doesnt address no cable modem, so, it doesnt finish installation.
All the computers can get ON the internet, BUT, none can see the gateway computer.
XP Pro is on all 5 computers. The gateway computer has the pci nic for the antenna and resultant associated software from the isp, and has a additional nic card cabled to the router internet slot.
What am I doing wrong??