Another media giant is bringing her act to satellite radio.

Oprah Winfrey said Thursday that she will program her own channel for XM Satellite Radio, including co-hosting a weekly show, in exchange for $55 million in cash.

Winfrey's three-year commitment, dwarfed by the five-year $500 million deal Howard Stern famously struck with Sirius Satellite Radio, highlights the fiece battle the two satellite radio firms have been waging in regard to striking programming deals and wooing subscribers.

But while Stern is expected to bring primarily young men to Sirius, XM is counting on Winfrey to encourage women to sign onto its service.

"Oprah is to women what sports is to men," said XM chief executive Hugh Panero. "There are media personalities, then there's Oprah."

Investors bid XM shares, which have been slumping for several months, 4.75% higher to $25.78.

The new "Oprah & Friends" channel will launch in September, streaming programming on health, fitness and other self-help advice and featuring several personalities familiar to Winfrey's TV fans, including Nate Berkus, Bob Greene, Dr. Mehmet C. Oz, Dr. Robin L. Smith and Marianne Williamson.

Gayle King, editor at large for O, The Oprah Magazine, will co-host a once-a-week, 30-minute XM radio show with Winfrey.

"Gayle and I have said for years it's a shame others can't be in on our conversations," said Winfrey, describing what the tone of her show will be.

Calling it a radio "reality show," she promised it would it would be a huge hit. "If I weren't me, I'd tune in," she said. She also said she'd pop up occasionally as a guest on other's shows on her channel.

Winfrey's career began in local radio, and she described her new XM relationship as "a full circle moment for me."

Panero said the deal calls for the construction of a radio studio in Chicago, where Winfrey and her Harpo media business are headquartered.

The arrangement also necessitates the creation of Harpo Radio, which will produce all of the content for "Harpo & Friends."

XM leads Sirius 6 million subscribers to 3 million, and Panero said that XM has not increased its 9 million subscriber year-end target as a result of signing Winfrey. He also said the cost associated with the new chanel won't affect his goal of making XM cash-flow break-even by year's end.

Winfrey is also expected to do at least some marketing on behalf of her relationship with XM, beginning Friday on her syndicated television show, when she and her "friends" discuss their XM plans.

She said, though, that her contract doesn't stipulate the amount of marketing expected of her. "I'm really free to do whatever I want," she said.

Asked if she'll hype XM to the extent that Stern did Sirius in the year preceding his jump from terrestrial to celstial radio, Panero said: "I don't think that's possible."

Panero also said that he doesn't foresee any other major content deals in XM's immediate future, having lined up Major League Baseball and other sports, along with celebrity talent like Bob Dylan and Ellen DeGeneres.

XM also has programming deals with such TV brands as "Good Morning America" and Fox News, though the latter is free to strike a similar arrangement with Sirius.

Panero said that Winfrey's deal also calls for XM and to split ad revenue generated from the channel 50-50 with Harpo Radio, an arrangement not unlike others XM has struck.

Talks between XM and Winfrey began in the summer when she visited XM headquarters in Washington, D.C. on the advice of Quincy Jones, Winfrey and Panero said. "There's not a content ditributor on the planet that doesn't call her up," Panero said. "Our culture and hers just hit it off."

Calling Winfrey "the anti-Howard," Barrington Research analyst James Goss said that XM needs only to sign about 200,000 additional subscribers to break even on the Winfrey deal, whereas Stern's deal with Sirius calls for about 1 million additional subs to break even.

In acknowledging that "Oprah is not the lightening rod that Howard Stern represents," he nevertheless reiterated his bullish stance on XM shares.

Likewise, Oppenheimer analyst Thomas Eagan called the Winfrey deal a "strong positive" for XM shares, guessing that XM need sign only 145,000 additional subs to break even. He estimated that XM's cost to bulid Winfrey's radio studio will be about $2 million.

"The deal does not seem overly expensive for what is considered by many to be a leading celebrity brand," echoed Bank of America analyst Jonathan Jacoby, who reiterated his $36 price target on XM shares.

Panero also noted that women are influential in about 50% of automobile sales, where most satellite radio subscriptions are sold, making Winfrey's presence on XM all the more important.

Along those lines, XM also anounced Thursday that Subaru of America will include XM radios in three of their 2007 models, including as standard equipment in the new B9 Tribeca Special Edition introduced Thursday at the Chicago International Auto Show.