Enable/Disable - SSRS Export Types

SQL Server Reporting Services (SSRS) supports to export different types like XML, CSV, HTML, PDF, etc., when you view the report.  This export option is available at report viewer Export drop-down list.
We can control this lists thru report services server configuration file which is available at "C:\Program Files\Microsoft SQL Server\MSSQL.2\Reporting Services\ReportServer\rsreportserver.config".
In This File, In <Render /> tag elements, add attribute Visible="false" and save the file. Now if you check, it won't be available at Export drop-down list
Example:
<Render>
<Extension Name="XML"
Type="Microsoft.ReportingServices.Rendering.XmlDataRenderer.XmlDataReport,Microsoft.ReportingServices.XmlRendering" Visible="false" />
</Render>

Hope it Help!