The secret word is "Klaatu Barada Niktu," though I'm sure that's not the answer you're looking for.
First things first: Do you have basic network connectivity? Can you ping the W2000 computer from the '98 computers? If you have IIS running on the W2000 computer, can you access it via IE/Netscape? Name resolution is also a factor: Remember that W2000 wants to use DNS, whereas '95/'98/NT4.0 rely primarily on NetBIOS name resolution by default...so see if a WINS server or an LMHOSTS file on the '98 workstation will help.
Second things second: I know you've checked NTFS & share permissions on the W2000 resource that you're attempting to access, but check them again. To rule out permissions as the source of the problem, temporarily set all NTFS and share permissions to "Everyone--Full Control"
This was first published in June 2002