Thanks for your suggestions,
I've done with it. Steps I've followed are
1. KILL the processes which is active / suspended / sleeping etc on the database :-D
2. Take the Database OFFLINE
3. Now copy the .mdf and .ldf to other machine.
and my whole requiement was deleting the current .mdf and .ldf files
restore new set of .mdf and .ldf files
connect those to the same database.
after the above 3 steps, i
4. deleted .mdf and .ldf files
5. deleted database
5. copied new .mdf and .ldf files into the location.
6. created new database with the same name.
and it works welllllllll