Laptop xchange shops???

I have a Compaq Presario 2000, which is working in perfect condition for the past 2 and a half years; however, I wish to purchase a new stylish laptop. Can anyone suggest me names of shops in Kolkata, especially in the Chandi Chowk area, where old laptops can be exchanged for newer ones.
It would be a real help if some body replies to my query.