She’s scored Number 1 singles and albums.  She’s won Grammys and Country Music Association awards.  She’s played countless shows before millions of fans.  But there’s just one venue where Carrie Underwood’s nerves will get to her — whenever she goes back to sing on the show that made her famous, “American Idol.”  Even four years after she won the “Idol” title, those butterflies got to her when she sang on this year’s season finale. (CLICK ON THE MEDIA BAR BELOW TO HEAR CARRIE UNDERWOOD)