There should definitely be a Vista Licence attached to the bottom of your laptop. Where did you buy it from?
Did you buy your W7 Ultimate upgrade? If you didnt then surely you must have realised it would be a dodgy copy. Just download an activation crack - I can get one over to you if need be. Saves the hassle of rolling back. And if you dont want a dodgy licence for W7, just buy a key off Microsoft and bang it into your dodgy copy, then it will be genuinely activated.