What song is this, and where can I hear it for free?

Question

It is on a comercial- there is a man singing first, then woman
Man: standing here beside you, want so much to give you this love in my heart, that I`m feeling for you, woman: you say im crazy, well i don`t care bout that, put your hand in my hand baby, don`t ever look back, let the world around us, just fall apart.. and so on, and so fourth

Answer 1

jefferson starship nothing's gonna stop us now

hear it here http://www.angelfire.com/pa5/patty5/NothingsGonnaStopUs.html