I'm going to assume you mean Peer to Peer networking. I'm going to walk through most of the steps to do this, but you may need to do certain things differently to accomodate for your setup. Follow these directions on both machines.
Also, I'm doing this from an XP/2k standpoint. Everything is a little different in ME but you should be able to do it.
right click on "my computer".
click on "properties".
click on "computer name".
click on "change"
set the workgroup to "workgroup" or whatever you want it to be. this IS case sensitive.
give each computer a unique name. the description is optional.
right click on network neighborhood
ensure that the computer has file sharing protocols installed
highlight tcp/ip and click properties and confirm ip addresses
-- side note -------------------------------------
develop a system for your IP addresses. this is an internal setting and can be anything you like. I'll show you what I do just to give you an idea of a good ip convention.
router -- xxx.xxx.xxx.001
external firewall -- xxx.xxx.xxx.002
file server -- xxx.xxx.xxx.011
service providing server -- xxx.xxx.xxx.012
my computer -- xxx.xxx.xxx.101
this way, I can parse any logs quickly and easily because my ip convention identifies the computers by putting them together by group. I have 5 more open ports that I can use for anything, like if some friends come over, and I can quickly assign IPs based on what they bring. ie., a friend coming over for some friendly games of Q3 gets xxx.xxx.xxx.102.
-- /side note ------------------------------------
If you're using a router, its IP address is your gateway for the computers (generally).
Make sure that all of the network cards are on the same subnet mask.
Your ISP will have information on the DNS servers you should use (if these machines are sharing an internet connection). If using the built in Internet Connection Sharing that comes with Windows, follow the instructions for that.
after all that you should be good to go with a reboot. if you still cannot "see" the other computer in your network neighborhood, try using the search utility. specify that you're looking for the other computer.
if you're still having problems, repost and someone should be able to help you. good luck!