I've never had to remove very heavy carpet staining, but a good wet and dry vac, with the right carpet shampoo, usually does a great job of cleaning and reviving carpets. I have this model:
http://i.imgur.com/fsERP0d.jpg
If you haven't already got one, just convince the other half that it's a good investment for cleaning household carpets and flooring
A Vax continuously pumps clean, warm water through the fibres, while lifting and brushing them. And the best bit is, when you've done you can turn the water off and use it to suck them dry (or, at worst, slightly damp).