Thanks to everyone who responded to my original inquiry. Follow-up as follows:
First, I was/am unable to use the rj-45 motherboard connections. No idea why???
Bought the Motorola cable modem and a linksys Ethernet router. (Was willing to go to expense of cables). Nothing worked at first, so I tried the USB connection which came with the router. It worked, so I knew I was good with Comcast.
Finally found an old Ethernet LAN board (from another life??) and installed in pc. Hey, it worked great. Went on and connected thru the router. (Had to go thru the setup sequence several times with the router before it recognized the internet connection??) Still worked, so went out and got another Ethernet LAN board for the second pc.
Cabled it to the router and we had simultaneous connection to internet.
All that remains is the laptop. From what I find using Google, I will need a RJ-45 Ethernet 10/100 USB 2.0 LAN adaptor for it.
Thanks again, Ace