Cannyman,
A window cleaner who rings me for advice now and again , rang last week to say he was going to buy a carpet cleaner.
I was busy driving so i said I'd get back and when i did I found he had researched steam cleaners and was about to buy something completely unsuitable for carpet cleaning.
The confusion arises partly because carpet cleaners sometimes claim to be 'steam cleaning' and partly because small domestic steam cleaners are sold as being able to do just about anything.
To clean carpet you will need a hot water extraction machine and a range of chemicals which are sprayed on prior to cleaning or as part of the cleaning solution.
Different manufacturers will obviously claim theirs are the best!
A steam cleaner is doubly unsuitable for soft furnishing , as not only will it not remove much dirt but it's use on thermoplastic fibres, nylon,polypropylene,acrylic etc is likely to cause irreversible pile distortion / realignment .
You don't say how far down the carpet cleaning road you are so I have assumed your new.
Fill in your profile and ask away.
Cheers,
Doug