James
Trust me there is an answer to this, we have linked servers between sql 2000, sql 7, sql 6.5, Oracle etc and we also had trouble like this but usually it was a login problem or setting etc.
What permissions does the SQL Server login on the SQL Server 7 box have? Make sure that it has atleast select rights on the tables.
Once you have checked the permissions, go back to the linked server> properties, security> select 'Be made with this security context'> Fill in the SQL 7 SQL user and its password as it is on the SQL 7 server> Go Okay.
Then right click on the linked server> refrsh> then see if the tables are visible?
Also try disconnecting complete from the sql server in EM and then connect again and see if you can see them.
EM in SQL 2000 doesn't always refresh the new objects properly.
John