Your Going to need a router. I reccomend the linksys 4 port cable\dsl router. Whats going to happen is your going to plug your dsl modems ethernet cable (that used to go to your computer) into the wan port of the linksys router. Then your going to take 1,2,3, or 4 and take an ethernet cable and plug them into computer 1 and computer 2. This is very simple. Also this is available in the wireless version. which would require the wireless router, and adapters for both computers.
Reccomend wireless for computers that are in differnt rooms becasue its easier.
P4 2.26 ghz, Intel d850emv2 mobo, 768mb of pc800, sony 4x dvd-rw, teac burner, nvidia ti4600 graphics, enermax 330watt ps
4 silent uv fans, cold cathodes in full tower antec case, round ide cables
SOny vaio 2.66 ht ghz modded into raidmax case with green cold cathodes.
P4 2.8ghz HT, 512mb ddr, Intel KD865gbfl, onboard video, raidmax case, blue cathodes, round ide, loomed wires, 4x dvd burner, wd sata 80gb hard drive
Intel d865perl, 2.8ghz northwood, antec sonata, wd caviar 20gb, Corsair 512mbx1 for now. 380watt psu, ati 9600, dvdrom cdrw floppy in black too match case