If you found that your sql server is slow and almost not responding to the request made by web application and you also observed that
CPU and Memory utilization at normal level. Then.

Here is how you can investigate

Open SQL query analyzer and fire below query to know how many number of connections opened to which database?

SQL query

select db_name(dbid) as DataBaseName , count(dbid) as No_Of_Connections , loginame as LoginName  from sys.sysprocesses 
                                                                                                                                        where dbid > 0
                                                                                                                                     group by dbid,loginame

By frequently running this query. You observed that the number of connections opened is high then there exist bug in your application
which didn't closed the opened connections. Stop the web application who uses that database and start over, system would run first
and later it suffers slow response then stops responding. In this situation you need to fix your application and not to blame SQL server.

Satalaj