Try Blue Magic Carpet Stain and Spot Lifter. That's what I've been using on our biege carpets. You can get it at KMART, AUTOZONE, or Chief's. However, my wife claims that the best method to clean very dirty carpets is to use a combination of clothing detergent, dishwashing liquid, water, and a bit ammonia. Wet the carpets with the mixture and scrub with a brush. Rinse well and then let air dry.