Special-effects-laden movies and Steven King adaptations used to be the most anticipated spectacles during May sweeps. Now, they stand in as programming cannon fodder, something to air when the nation turns its eyes to the last night of competition on “American Idol” (7 p.m., Fox) between Taylor Hicks and Katharine McPhee.

Not so long ago, Fox would have padded out the final sing-off to two hours, partly to crush the competition and partly because Fox didn’t have much else to air. But tonight’s “Idol” leads into the season finale of “House” (8 p.m., Fox). The medical drama about a dyspeptic physician has become a bona-fide ratings sensation in its own right. In the week ending May 7, “House” was the fourth most popular show on network television.

On tonight’s “House” finale, a former patient (Elias Koteas) shoots House. Presumably, he didn’t understand the acerbic irony behind some of the doctor’s remarks. To add insult to injury, the cranky MD must share a hospital room with his assailant.

Based on a novel by Steven King, the three-hour thriller “Desperation” (7 p.m., ABC) offers a long, strange variation on an old “Twilight Zone” theme: the deserted rural town where visitors check in but can never leave. Ron Perlman has a great time hamming it up as Collie Entragian, a deranged state trooper with a nasty skin condition and the habit of planting evidence on drivers he pulls over on a lonely stretch of Nevada highway. He barks out strange incantations in some ancient language, has a special affinity for wolves and buzzards, and kills some victims and imprisons others.

Soon he has a motley collection of souls in his jailhouse, including Johnny Marinville (Tom Skerritt), a famous best-selling author who decided to discover America on his motorcycle while followed at a safe distance by a loyal go-fer, Steve Ames (Steven Weber), driving a moving van with all of the comforts of home.

Just who or what is in possession of Collie? What’s happened to the doomed mining town of Desperation? One thing is certain: “Desperation” is filled with inside references to King’s other shockers, including the word “R-e-d-r-u-m” written in blood on a jail wall. And with Skerritt’s character, King is clearly not afraid to make a little fun of himself.

¢ This time last year, Carrie Underwood was on the verge of winning “American Idol.” Tonight, she’s competing with it, appearing on “The 41st Annual Academy of Country Music Awards” (7 p.m., CBS). She’ll share the stage with Trace Adkins, Big & Rich, Brooks & Dunn, Kelly Clarkson, Kenny Chesney, Toby Keith, Miranda Lambert, Martina McBride, Brad Paisley, Rascal Flatts, Sugarland, Sara Evans, Montgomery Gentry, Keith Urban and Gretchen Wilson.

Tonight’s other highlights

¢ Community service for Rory on “Gilmore Girls” (7 p.m., WB).

¢ Pampered teens rise to the occasion when the family’s fortunes turn in the 2006 TV feature “Cow Belles” (7 p.m., Disney).

¢ Kim Delaney stars in the conclusion of “10.5: Apocalypse, Part II” (8 p.m., NBC).