Ashley Tisdale shot to fame as Sharpay Evans in the High School Musical movies. But with the third movie not due until October, she has taken another step to stay in the public eye. A misstep, I should add.

It's called Picture This, and it gets what Fox is calling ''its world premiere'' on DVD on Tuesday for $26.98. That's a very polite way of saying it's a direct-to-video release that doesn't take the risk of theatrical screenings.

But it's as home viewing that this tepid comedy is slightly palatable. In a theater, I would have been snarling before the end. At home, I could at least fast-forward.

Tisdale, who is also an executive producer of Picture This, plays Mandy Gilbert, a high school student who is trying to deal with an overprotective father (Kevin Pollak), an utter lack of social status and her so-far-unrequited passion for hunky Drew (Robbie Amell).

Things seem to be on the upswing when Mandy gets a new cell phone and contact lenses, and Drew starts paying attention to her. But she then has to contend with a school rival, being grounded and whether Drew's intentions are honorable.

Not to mention that she absolutely has to sing. Shadows of the Night. Yes, the Pat Benatar song. Tisdale can sing, but this was better left undone.

Anyway, it's fluff, erratically paced and with mixed social messages and scenes where Tisdale just cannot hide that she is 23 years old.

DVD extras include a making-of segment and a trivia game.

Coming to DVD from the big screen is the surprise hit 21 (Sony, $28.96 on standard-format single disc, $34.95 in ''2-disc deluxe edition'' and $38.96 in high-definition Blu-ray). Based on Ben Mezrich's book Bringing Down the House: The True Story of Six M.I.T. Kids Who Took Vegas for Millions, the movie stars Jim Sturgess as a student brought into the gambling team, Kate Bosworth as a teammate and love interest, and Kevin Spacey as the team boss.

The book wasn't that great but still superior to this tepid affair. Director Robert Luketic knows how to make scenes look interesting — the movie did have me wanting to go back to Las Vegas — but Sturgess is a wan presence in the middle of a story that seems to have lost whatever was most interesting in Mezrich's book.

You should also note what my colleague Daniel Fienberg of Zap2it.com said: ''Until two-thirds of the way through the book, all of the members of the card-counting team are part- or all-Asian. So Hollywood adapts Mezrich's book and it's about two attractive white kids flirting.''

Extras on the single DVD include a director commentary and several featurettes. The two-disc version adds a digital version for downloading. The Blu-ray has a ''virtual blackjack'' game.

As long as we're talking about Las Vegas, Tuesday will also bring Las Vegas: Season Five (Universal, 18 episodes, $59.98). This was a transitional year for the show, with James Caan easing out and Tom Selleck coming in. But it also proved to be the final season, and a huge disappointment for fans, since production was shut down before many story lines could be wrapped up.

Nor does the DVD provide any relief. It includes some extras: webcasts done during production, a piece on the visual effects, a montage of highlights from the show and a gag reel that suggest how very, very close Danny (Josh Duhamel) and Mike (James Lesure) could have been. But there's no indication of how the show's cliffhangers might have been resolved; the last episode still includes a ''to be continued'' note.

Since I've been a little cranky about the DVDs discussed so far, I should mention one that I liked: Spaced: The Complete Series (BBC Video, 14 episodes, three discs, $59.98).

All I have to tell some of you is that it was co-created by and co-stars Simon Pegg (Shaun of the Dead, Hot Fuzz). For everyone else, it's a very funny show with Pegg and Jessica Stevenson (now Jessica Hynes) as a couple of aimless people who fake marriage to get an apartment together.

It's a tired premise, but execution is everything, and Spaced veers into odd directions, tosses off jokes right and left and offers an array of amusing supporting players. And when you're done with the episodes, the extras are piled on: tons of commentaries, a documentary, outtakes, a show reunion and more.

Emmy notes: If you are looking for recent Emmy nominees on DVD, you can find plenty. John Adams, the most nominated show overall, is on DVD, as is the first season of Mad Men, the most nominated drama series.

30 Rock, the most nominated comedy, has its first season on DVD. The second season, which just scored at the Emmys, is due in October.