[Jack Simth]

It's been a while, and I'm doing this from memory; I may be missing a few steps...
Right-click Network Neighborhood
select Properties on the context-sensitive menu
Select TCP/IP on the list
Click Properties
Move from "Obtain an IP address Automatically" to "Use a specific IP address" (or whatever it's called)
Put in the numbers appropriate to your network (the IP address itself needs to be unique, but you can clone the rest off of another machine on the network - open up command.com (start/run, enter command.com) and type in ipconfig - that should get you most of it)).
Hit Ok/close out of everything, reboot.

Edit: Oh yeah - and while the IP address has to be unique, you don't want to change more than the last number on most networks. It still has to be in a particular range, which is specified by the net mask.