Have to echo the recommendation for this software. I found it while trying to do the exact same thing you're trying to accomplish. I downloaded the demo, got my song, converted it into an MP3 and was quite happy.
Then, a couple weeks ago I just went and paid for the ap. It's that good. I think you'll be happy with it.
There is another software -- I want to say it's called wiretap but I wouldn't swear to it and I don't have time to do a search -- that also does this and I am nearly certain that it's free.
So look for that, too.