What is(are) the clustering column(s) on the table? You need to read each 1/4 of the table at a time using the appropriate clustering key range.
What are there nonclustering indexe(es)? (in case they are needed to determine the clustering key ranges).
SQL DBA,SQL Server MVP(07, 08, 09) A socialist is someone who will give you the shirt off *someone else's* back.