According to industry scorekeeper SoundScan, "Oops" has moved an amazing 1.3 million units in seven days. It will debut next week at No. 1 on the Billboard album chart, which should make her 17 credited producers proud.

"Oops!" follows Spears' nine-million selling 1999 debut "... Baby One More Time." Not bad for a former Mousesketeer whose solo career began less than eight quarters ago on a mall tour, singing to blue-haired shoppers at food courts.

Once upon a time, these numbers might have ensured a lengthy stay in the No. 1 slot.

Incredibly, Britney must watch her back. In a twist straight out of a WB high-school drama, a pot-smoking derelict who sneaks peaks of cheerleaders under the bleachers is about to ruin her big night out. White bad-boy rapper Eminem is poised to evict Spears from the top spot with his own putative blockbuster, the aggressively violent and demented "The Marshall Mathers LP."

According to music retailers nationwide, the "Marshall Mathers LP" (a follow-up to Eminem's triple-platinum 1999 debut, "The Slim Shady LP" ) will also break the million sales mark next Wednesday. "It may be the biggest rap record we've ever sold," reports David Lange, owner of New Jersey music chain Compact Disc World.

Which means Eminem (born Marshall Mathers) will almost certainly evict Britney -- whose sales numbers are bound to dip during the second week -- from the No. 1 slot after seven days. "I'm expecting 'Mathers' to do between 1.2 million and 1.4 million," says John Grandoni, vice president of purchasing for National Record Mart , which owns 181 record shops nationwide.

Regardless of who ultimately wins the Britney vs. Eminem event, it's the music industry -- justifiably nervous about a future filled with online predators -- that will be the big winner. If Eminem meets expectations and sells one million copies by week's end, it will mark the first time in history that the industry has enjoyed back-to-back one-week million-sellers.

In fact, only five albums have hit that seven-day plateau since SoundScan began scanning countertop data in 1991: the soundtrack to "The Bodyguard" featuring Whitney Houston, Garth Brooks' "Double Live," the Backstreet Boys' "Millennium," and 'N Sync's "No Strings Attached" (which sold an unsurpassed 2.4 million units in its first week). And now, Britney's "Oops." The last three titles were all released by Jive Records -- all within the past year -- much to the consternation of other labels.

Britney vs. Eminem continues an epic battle between the twin engines driving today's music business: innocence and evil. Behind these front-runners, shoppers continue to line up for Christina Aguilera and Mandy Moore or hard-knocking porn lovers like Kid Rock and Limp Bizkit.

Falling between the cracks are the acts formerly known as alternative. Pearl Jam, a band that once flirted with a million-selling week, saw its latest album, "Binaural," debut at No. 2 behind Britney's "Oops!" Problem was it sold 1.1 million copies less. The new No Doubt CD, "Return of Saturn," is languishing at No. 24. And how fitting that Billy Corgan, lead singer of the Smashing Pumpkins, announced the band's official demise ("The way the culture is and stuff, it's hard to keep trying to fight the good fight against the Britneys. ") a day before Spears' record-setting numbers were posted.

With all due respect to Mr. Corgan, it may simply be that Britney works a bit more. A leading candidate for Hardest Working Post-Pubescent in Show Business, Spears has become an industry unto herself. A partial list of her recent and upcoming TV and magazine-cover appearances: "Late Night with Conan O'Brien," "The Rosie O'Donnell Show, "The View," "Nickelodeon's All That," "The World Music Awards," "Britney in Hawaii on Fox," "Today," "The Tonight Show with Jay Leno," "MTV's Total Request Live," "MTV's Beach House," "MTV's Britney Weekend," TV Guide, Rolling Stone, Cosmo Girl and Allure.

"As hard as she works, I'm surprised she hasn't lost it," jokes Tom Calderone, MTV's senior vice president of music and talent programming. "Her manager had her touring during the month of March when her album was still being tweaked." MTV clearly profits from Britney and Co. The cable giant's ratings are up 20 percent during the first quarter of this year compared to '99.

With the help of Jive Records labelmates Backstreet Boys and 'N Sync, Britney's influence extends to other arenas in the music business. At Top 40 radio, where Spears has been a daily fixture for the past 19 months, times are good. According to Billboard's quarter ratings analysis, listener share has increased from 8.8 percent during the summer of '98 to 9.9 percent in summer of '99. (This year's figures are not yet available.) During that same period, all-important teen listening jumped from 29.9 percent to 35.2 percent. Meanwhile, the stations are getting crowded: The number of mainstream pop broadcasters in top markets has increased from 126 in '97 to 168 last year.

Concert promoters -- along with her corporate sponsor, the California milk-processor "Got Milk?" campaign -- are salivating for Britney's sold-out summer arena tour, even if the singer is guaranteed to pocket a cool $400,000 per night. (If Mariah's wondering why Britney just trumped her, the diva might compare their touring schedules : Mariah agreed to half-a-dozen concert dates this spring; Britney is scheduled to do sixty North American shows between June and September.)

The Britney juggernaut continues: Her recent hosting duties on "Saturday Night Live" delivered the show's second-highest ratings for the season. Even McDonald's franchise owners love her: The chain is hosting a Britney Spears concert vacation contest. (Rival Burger King's already signed on to sponsor the Backstreet Boys' fall tour.)

Such is the bubble-gum backdrop that Eminem must contend with. But his unfolding sales success is perhaps even more startling. Eminem's record-breaking numbers will come despite the fact that some retailers refuse to stock his R-rated album (even though a so-called 'clean,' stickered version is available).

Eminem's secret weapon is his unusually strong crossover appeal. Thanks to producer Dr. Dre's instant credibility, Eminem enjoys Top 10 status at hip-hop radio; meanwhile, his (white) outlaw image earns airtime on alternative-rock radio. And thanks to a killer chorus that tests well in listener research, Eminem can be heard on Top 40 stations. In fact, just three weeks after its release, Eminem's middle-finger anthem "The Real Slim Shady" is already racing past Britney's single on mainstream pop stations. (Her one advantage? She's No. 1 on nationally syndicated Disney Radio , where Eminem doesn't make rotation.)

Four weeks from now, the dust will settle, and it will be clear which formula brings bigger sales. For the industry, the dream scenario is that all those Britney fans open their wallets for Eminem.

"I'm pretty sure 12-yeard old girls who buy Britney will buy Eminem," says Kevin Engler, senior music buyer for the discounting Best Buy chain. And what happens when new, unsuspecting fans bring home "The Marshall Mathers LP" and journey beyond Eminem's Top 40 single to discover the rest of his defiantly foul-mouthed world? Says one label president: "They're going to shit their pants."