Changing SQL Server 2000 usernames
Some notes


When you create a login, then the name must match AD exactly
EXEC sp_grantlogin 'DOMAIN\Andy Soell
When you map the login to a database user, it can be renamed
EXEC sp_grantdbaccess 'DOMAIN\Andy Soell', 'Dilbert'


The 2nd bit will fix your issue with implied schema. This happens if don't qualify schema (eg dbo) because SQL Server 2000 has pretty much no user-schema separation like later versions

Note: you can't rename users in SQL Server 2000 IIRC: need to run sp_revokedbaccess then sp_grantdbaccess. If you own objects because of your implied schema then you'll need sp_changeobjectowner. I think SQL EM will prompt you.

That is, you should always qualify schema in SQL Server.

CREATE TABLE dbo.viewname...

SELECT * FROM dbo.myTable

EXEC dbo.MyProc


Then no need to change the users