When using SQL Server 2000 and the user doesn’t have sysadmin rights, and their login isn’t mapped to the dbo user within the database all objects created will be, by default created under the user schema.
This is the normal behavior of SQL Server 2000. In order to allow users who are not members of the sysadmin fixed server role to create objects under the dbo schema by default you have to map their login to the dbo user, even if they are a member of the dbo fixed database role.
To work around this, in the T/SQL code specify the owner of the database object. If your developer is using Enterprise Manager to create the new tables before saving the table, click on the properties button in the upper left hand corner of the Enterprise Manager window (second from the left). Then change the owner drop down from their username to dbo. There is no way to default this setting to dbo so it will need to be changed for each new table being created.