NBC is betting that video streams will help its on-air primetime ratings rebound from last season’s doldrums, as it’s making preview episodes of several shows available online and on mobile platforms for one week before their network debuts.

The shows are being streamed on www.NBC.com, the NBC-owned www.Hulu.com and through Hulu distribution partners Yahoo, MSN, AOL, MySpace and Fancast.com. Episodes are also accessible via Xbox Live on Xbox 360 and through Microsoft’s Zune player.

NBC started streaming the first episode and pilot of new series “Knight Rider” and the opener of “Lisptick Jungle” last Tuesday in advance of their on-air premieres tomorrow night. First episodes of “Life” and “Chuck” start streaming today, with the pilot of “Kath and Kim” up next on Oct. 2, followed by “30 Rock.” “The Biggest Loser” was also streamed prior to its season debut last week.

Yahoo will also stream pilots of “Kath and Kim,” “My Worst Enemy” starting Oct. 6 and “Crusoe” starting Oct. 10, one week prior to their respective on-air premieres.

Comcast, Cox, Charter, Dish Network, and Verizon Fios TV are also running the previews on their respective video-on-demand services.

NBC is also posting clips from other series on the non-traditional platforms, including AT&T Wireless and MobiTV, which will carry the “NBC Primetime Preview Show.”

“For a promotional purpose it’s brilliant, to get some buzz going,” said media analyst Gary Arlen. “But preview showing begins to bend what platform it’s aimed at.”

John Miller, NBC chief marketing officer, said, “The goal with the sampling program is to increase on air viewing of the series. Exposure to the show or messages promoting the show achieve that.”

Miller said the network was not specifically targeting younger viewers, but acknowledged that might be the result from serving up video streams. The new and returning series selected were those that the network thought could most benefit from sampling. “The benefit of the sampling programs is that we get significant exposure from each venue which promotes the content offering,” Miller said.

Arlen said the tactic is obviously a ploy to push sampling— and TV ratings—among younger viewers in the wake of NBC’s also-ran performance during the past TV season. He noted that Nielsen Media reported in May that all age categories are now watching some video online, although the prime online video audience is adults 18-24, who watch an average of an hour weekly.

“It doesn’t mean they’ll watch a 20-minute TV show,” Arlen said.

NBC is certainly hoping that they’ll stay for more than a trailer-sized sampling, but the widespread sampling it’s enabling figures to have some impact on initial ratings returns.

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