There is no such thing as an administrator logon on Win98se because there isn't really any security.
Here is a
FAQ on Anandtech. Here is another
FAQ on DSLReports about sharing. Check those first.
Can the Win2k machine at least get files from the shared folders on the Win98 one? If not are you using a login or does it just go into windows on boot up? You need Client for Microsoft Networks installed in your network settings. You also need to have file and print sharing enabled on the Win98 machine and have a login with a password (not a blank one).
If you can't get files from the Win98 machine try this. Create logins on both machines that are the same, on the Win2k machine set that users permissions to administrator. Make sure your using a password on both accounts, it may have to be the same password too. You should be able to share folders now, if this doesn't work go here.
DSLReports Network Forum
They helped me when I was having problems sharing with 2 WinXP machines. Had to turn off simple file sharing and some other things. They know what their talking about. You can post without making an account too, but it's quick and easy to create one. You can probably do a search and find your answers.