It's the RSReportServer.config file. Change the <render> element by adding Visible = False to any entry you don't want to support.
Note: The above information comes directly from HitchHiker's Guide to SQL Server 2000 Reporting Services, page 155.
Hope this helps.
Catadmin - MCDBA, MCSA
"If a person is Microsoft Certified, does that mean that Microsoft pays the bills for the funny white jackets that tie in the back???