I would have to agree with Trellum that Rosetta Stone is very expensive. That are lot of cheaper ways of learning German. I personally attended German Classes in Chennai at a place called FITA and it was good. In fact your travel expenses and the course fee put together would be cheaper than what you probably pay for Rosetta Stone. I think they offer Online German Classes also. Do check out their website, they may be of help for you.
Here is their website: http://www.fitaacademy.com/courses/german-training-classes-in-chennai/
Thanks
Mike