carpet odor

How do I get old odor out of my carpet to make my house smell fresher?
warm house makes the odor in the carpet come out?
I recently purchased a house with obvious cat odor in the living room (I got a discount to pay for carpet replacement.) Before replacing the carpet, I tried Simple Solution Stain and Odor remover. I really soaked the carpet and the smell is gone. The stuff is great on carpet and laundry stains too. It totally removed a magic marker stain on a white carpet.
I buy the product at Petsmart, but I think you can get it at any large pet store.