Home Telephone Neworking

The easiest way would be to run a Cat5 crossover cable between the 2 computers.
You will need to install direct cable connection in network options on both machines.
If they are some distance apart, install Cat 5 wall jacks in each room with Cat5 cable running between the rooms. Connect one PC to the jack with a normal Cat5 cable, and the other with a crossover cable.

If you want to use the standard phone line, you need different network cards. I know that both Diamond and Linksys make phone line networking hardware.
A reference site for phoneline networking is www.homepna.org

why dont' you get a little 4 port netgear hub
they are cheap - do the job.

I know this isn't a phone network, but it'll do the job.