Report Viewer in Configuration Manager 2007 limits the number of rows returned to 1,000 rows when you click Values and the values list displays for a prompt. The maximum number of rows returned by the query for the prompt that populates the values list can be modified by creating a registry key and setting a value on site system computers that have the reporting point role. IMPORTANT : Increasing the maximum number of rows for queries that return a large amount of data or for queries that are inefficiently...(read more)

Read the complete post at http://scug.be/blogs/sccm/archive/2009/09/30/sccm-2007-reporting-how-to-change-the-maximum-rows-returned-in-the-values-list-that-is-default-set-to-1000-rows.aspx