One system is getting slower and slower, so I decided to use profiler for investigation.
Googled and read out the following useful articles:
http://serverfault.com/questions/162245/how-do-i-identify-slow-queries-in-sql-server
http://www.codeproject.com/Articles/21371/SQL-Server-Profiler-Step-by-Step
to minimize changes to production, I select using tracing file instead of a table.
confirmed with below two articles for finding out indexes columns.
https://bytes.com/topic/sql-server/answers/562317-how-do-i-find-indexes-columns-sql-server-2000-a
http://stackoverflow.com/questions/765867/list-of-all-index-index-columns-in-sql-server-db
Finally, I got a huge return -- the system has ZERO indexes created.