E.G.
I found Spot Shot works great on old stains. but someone else had a good point... depending on where you are renting from, and how long you you have lived there - you might want to talk to the landlord. one of the rentals we lived at automatically replaced the carpet because it was over 2 years old when we moved out - we didn't even have to clean the carpet since they were just going to toss it anyway.