First, if you want to share parts of your MacOSX, I highly recommend SharePoints. MacOSX only allows remote login and the shared folder. If you want to share a "music" folder, for example, SharePoints will help you do it.
If you are on a network with XP, and it is having trouble finding you, try typing in your IP address into a browser window (ie "\\192.168.1.101\"). This should open a window with all your shared folders visible. If that works, then you can also go into the Network folder, add a Network Connection, then type in your IP address and the folder that you want to access (\\192.168.1.101\folder\).
Your IP address can be located in System Preferences - Sharing. At the bottom it says something like, "Remote users can access your computer at \\192.168.1.101"
I'm still trying to figure out how to network 2000 with MacOSX. I can see my computer, but when I try to log in it only prompts for a password instead of a user name and password. Any help on that would be appreciated. Preferably without downloading third party software.