OK, you have selected the Folders or Drives (essentially folders) that you want to share. i.e. Right Click on a Folder and Select Sharing (in Windows 2000) or Sharing and Security and the set the folder as Shared?
One minor note in this, to work properly in Windows XP Go, My Computer -> Tools -> Folder Options -> And UNcheck Simple file sharing. Makes things a whole lot easier!
Yes, UNCHECK.
Then voila. Things should work as planned.
Hope this helped