When you say 7/22/2012 it will take records before 7/22/2012 00:00:000
So you have to say either '7/23/2012' or '7/22/2012 23:59:59'
select top 2000 Time_Stamp,LATITUDE,LONGITUDE,LOCATION from tablename where TIME_STAMP between '07/14/2012' and '07/23/2012' group by Time_Stamp,LATITUDE,LONGITUDE,LOCATION order by Time_Stamp desc
or
select top 2000 Time_Stamp,LATITUDE,LONGITUDE,LOCATION from tablename where TIME_STAMP between '07/14/2012' and '7/22/2012 23:59:59' group by Time_Stamp,LATITUDE,LONGITUDE,LOCATION order by Time_Stamp desc