Netix,
I found the real carpet cleaning stuff (made by sabco or similar) is better than the preen stuff. It has been around for years and does the same thing but better. I think my mum used to use a powder one for spot cleaning and that was quite good.
don't know where you live but this suggestion is only good for warm climates where the rug can dry. We used to take the rug outside, drape it over DD's climbing thingy and spray it with floor cleaner and then spray it with water and get a broom and give it a scrub with the broom. then spray with hose to rinse it. gives it a very thorough clean but takes a while to dry so needs to be a nice sunny day. Also we don't do that since the water restrictions as it uses heaps of water but comes up like new, especially if you spot clean before.