How to recover Windows Vista?

Okay. Well my dad paid his friend to fix our HP Computer because it was going slow. After he "fixed" it I noticed that the corner of the computer it said wasn't legitimate or something like that. The a couple of days ago when I started up my computer it said that the activation has expired and that I must re-install. So on the hardware monitor there is a sticker of the Windows Vista activation key. When I tried to type it in it said it was wrong so I went to the computer properties and it said Windows 7. I'm guessing this man installed it but it wasn't the actual windows 7. I don't know the activation key to this and my dad hasn't been able to get a hold on him. The computer already came as Windows Vista when we bought it and I don't know if it came with a recovery disk, if it did well I cannot find it. Is there anyway I can go back to Windows Vista without paying anything and still save all my music? Thanks!!!