Report Viewer Web parts for SharePoint
Two types of Report Viewer Web parts are available :
1. Web Parts which come with SQL Server Reporting Services
2. Web Parts which come with the Reporting Services Add-in for Sharepoint
Though both web parts have same name the difference between them is that the web parts which come with the add-in will work only with Reporting Services in SharePoint Integrated Mode.
The web parts which come with SQL Server Reporting Services work with Reporting Services in native mode.

The SSRS web parts can be found on the server where Reporting Services is installed. The default location is “C:\Program Files\Microsoft SQL Server\90\Tools\Reporting Services\SharePoint\RSWebParts.cab”. To install these web parts, copy the RSWebParts.cab file on the SharePoint Server and run the following command at the command prompt.
“STSADM.EXE -o addwppack -filename "RSWebParts.cab" -globalinstall