Slow queries on SQL Server We have SQL Server 2005. Our main table is the archive table which has nearly 200 million rows in it. There are 2000 clients that connect a service so the service writes the information to the archive. We have also another service which gets the clients information from archive as batches and calculate some another information for each row and rewrite them as batches again. 

On the webhand-side we have 100-200 users online at a time and most of the queries depends on archive table. I built all possible indexes on archive and I'm using .NET Framework 3.5. I am connecting the database with standard connection string.

The problem is when a user request for one day long report it returns in 10-15 seconds for 50 rows. The one month long reports take more time like 2-3 min for 5k-6k rows. I am not a DBA but we don't have one so i am expected to tackle this problem. Can you make any suggestions for my problem?

Thanks.
As you didn't provide us with any detailed information, may I suggest you watching the following videos from Brent Ozar (Very smart MVP). 


  http://www.toadworld.com/platforms/sql-server/w/wiki/10063.find-missing-indexes.aspx
  
  http://www.toadworld.com/platforms/sql-server/w/wiki/10062.find-indexes-not-in-use.aspx


These videos will give you a basic idea of how indexing works and give you scripts to run against your database and check for missing indexes and indexes that are not used.

I hope these links can help you, as they did for me.