Home Computer Network Confusion

We now have 2 home PCs, within 25 feet of each other, in adjoining upstairs rooms. One is a Dell Dimension 2400 with Windows XP, Service Pack 2, 2.2 Ghz Intel Pentium 4, 40 GB hard drive, 1022 Mb memory, Broadcom 440x 10/100 Integrated Controller
and one is a Dell Dimension E510 with Windows XP, Service Pack 2, 2.8 Ghz Intel Pentium 4, 160 Gb hard drive, 512 Mb memory, Integrated 10/100 Network card
Through our one ISP, we have VoIP and DSL, with a Linksys SPA 2010 phone adapter with router and a Westell 6100 router--BOTH from ISP, and installed via the Dimension 2400, which I'd like to continue using as host computer).

The SPA 2010 has only one Ethernet port, cabled to the Network connection port in the computer. The SPA 2010 has one Internet port connected by cable to the only Ethernet port of the Westell. The SPA 2010 has Phone1 port with phone wire to baseboard jack. The Westell has only one Ethernet port connected to the SPA as already mentioned. The DSL port of the Westell is connected by a thin wire to another baseboard jack. I want to network the 2 computers, for Internet use, so I bought a Linksys WRT54G router. (Why the router?--silly me, I thought it would be easier than hubs or switches). I am unable to get Internet connection or phone dial tone when I set the WRT54G up with the Westell and the SPA 2010 as instructed on the WRT54G CD setup. I was able to do the rest of installation on the CD, but when I got done, I got the error message that there is no recognition of a connection to the Internet. My hunch is that there is a conflict between one or more of the routers. Have read extensively on Internet but there is no clear answer.
Please advise. Thank you.