The show is called "American Dreams" and the episode with Vanessa Carlton airs on February 9. Here's the info from the NBC site:
Heartache: Vanessa Carlton guest stars as Dusty Springfield (and sings Springfield's 1964 hit "Wishin' and Hopin'") on a Valentine's Day-themed episode that's short on romance. There's a dance at East Catholic, but Luke (Jamie Elman), true to form, is ambivalent about attending. And Roxanne doesn't have a date. Neither does J.J., because Beth won't return his calls. Meanwhile, Patty is planning her first boy-girl party, but Helen sees to it that opportunies for romance will be few and far between. And in another matter of the heart, Jack is having chest pains.
