Right i sent a song to my gf over msn and when she got the song it wouldnt play, said somthing about its locked/blocked to protect her computer.

So i told her to right click on the tune go to properties and then to look on the box near bottom for a word that says unlock, because this is what i did when a song was blocked on my pc, but on hers she hasnt got an unlock option so what can we do to make it play? and it wasnt like the song i sent was locked either, it played straight away fresh from download on my pc?
I downloaded another song after and sent that but it was exactly the same.

Any ideas?