I took Spanish in high school. However, natural immersion was impossible - so it didn't amount to much. In fact, there wasn't even any replacement for it - like software. Anyway, my next experience with language came in South Korea - and I got natural immersion there - rather I wanted it or not! However, though, I wasn't trying to learn the language much - besides the fact I learned Hangul - the alphabet.
So, who has tried immersion software like Rosseta Stone or something? Myself, I've never tried anything like that - but it sounds very interesting, though, too expensive at the moment!