|I quickly checked this tutorial and it seems good. (Plus it'll avoid having me type one here from scratch...)
One thing that seems to be assumed in this is that the computer names and workgroups are properly set from the start, which isn't always true...
You'll usually want all your computers on the same workgroup and with names that have some sort of a meaning. To check that these setting are alright (in Windows XP), right-click the My Computer icon on the desktop, then Properties, then the "Computer Name" tab (my Windows here is in French). You should have a "Computer description" field, in which you can basically write some comment that will be visible from other computers below are two buttons, the first that launches the network setup wizard, and the second that allows you to modify your computer's actual network name and workgroup.
Hope that helped, and let me know if you have other questions,