IF YOU COULD GO BACK TO YOUR teenage years and correct the life-altering mistakes you made then, which decisions would you change?

For Matthew Perry?s 37-year-old character in ?17 Again,? the bone of contention is his precipitous fall, from the winner that he was at 17, to the loser he has become.

What went wrong? When he was a high school senior, he was a basketball hero headed for a big college scholarship, but he had to give everything up to peremptorily marry his sweetheart.

Flash forward 20 years and two children later, the fallen hero is trapped in a dead-end job?and his wife has decided to divorce him, because love no longer vivifies their marriage.

Luckily, at this lowest point in his life, Perry?s character is zapped by the helpful finger of fate and retroactive remorse?back to his teenage years, during which he?s played by Zac Efron (who doesn?t look at all like him, but director Burr Steers must have thought that was of little consequence). Wrong.

Another bone of contention is the movie story?s generally predictable progression, with viewers often second-guessing the storytelling?s twist and turns, like the Perry-Efron character?s belated efforts to help his teenage kids solve their many problems.

Happily, the plot?s predictability is salved by the energetic and felt performance turned in by Efron as the teen persona of the remorseful husband and father.

The talented young actor goes beyond the usual teen gimmicks and bothers to depict the retro-dad?s conflicted feelings.

Efron is so effective in the role that his performance in ?17 Again? can be seen as his breakthrough role as a leading man. The character he plays is still a teenager, like his roles in the ?High School Musical? and ?Hairspray? productions, but it?s deeper and more textured due to its ?invisible? but still palpable adult component.

?17 Again? may lack originality, but it?s viewable for its casts? perky ensemble work. It also inspires moviegoers to get a hold of their lives, learn from their own mistakes, and do what they can to correct them?even without the benefit of a magical, cinematic sleight-of-fate.

Four ?AI? survivors
Last week?s ?American Idol? finals round was predictable in one sense?Matt Girard was booted out?and a shocker in another: It was the first time that consistent front runner Adam Lambert ended up in the bottom three.

With Matt out, the field of survivors has narrowed down to only four?three men (Lambert, Danny Gokey, Kris Allen) and a solitary young woman (Allison Iraheta, who?s just turned 17).

Now that there are only four remaining contenders, it?s interesting to see how much more clearly the surviving finalists have been presenting themselves as unique performing artists:

Lambert is the theatrical performer with fantastic vocal range?he puts on a big show each week and keeps surprising viewers with his prismatic presentation of his abilities.

Gokey is less flamboyant, but has also learned to put on a show. Lone female survivor Iraheta is the tilt?s power singer, but has also learned to feel her songs, imbuing her with intimations of an artistic maturity beyond her years.

The big surprise is Allen. He started out as a Danny Osmond clone, but has since ?messed up? his bland boy-next-door image, complete with five o?clock shadow and all.