New York- Late yesterday, Hilton canceled what had been scheduled to be her first interview since sexually explicit vide tape of her having sex were leaked to media outlets and made their way onto the Internet.

"Late Show" staffers seemed to be the last to find out she was pulling out.

Representatives of the show had spent the morning publicizing her upcoming appearance -- only to have Paris Hilton pull the rug out late yesterday afternoon.

Hilton had been booked to appear on the show next Wednesday to promote her upcoming reality show, "The Simple Life."

Behind an unlabeled door in a building along Eastlake Avenue East lives the Marvad Corp., a lucrative online empire of Internet pornography sites that have made the owners rich men.

And until about a week ago, the unobtrusive office, in the same building as a chiropractor's office, was home to one of the few copies of a videotape showing Paris Hilton, the 22-year-old hotel heiress and reality-TV phenomenon, having sex a few years ago with her boyfriend at the time.

"You walk in there, you'd think it's an insurance office," Kevin Blatt, Marvad's publicist in San Diego, says with a laugh.

As anyone who regularly watches the E! cable channel knows, Hilton's ex-boyfriend, Rick Solomon, best known for being married briefly to actress Shannen Doherty, sued Marvad in federal court in Los Angeles last week, alleging the company had no right to post the video on the Internet and charge people about $29.95 each to see it.

In turn, Marvad sued a man named Donald Thrasher, 33, an acquaintance of Solomon's who somehow got a copy of the tape and sold it to Marvad for $50,000 plus royalties. Marvad contends Thrasher had falsely claimed to have rights to the X-rated video.

Also, Solomon has sued Paris Hilton and her family, alleging they defamed him by portraying Hilton as a rape victim and unwilling participant in the on-camera sex when she was 19.

Marvad finally agreed to give the tape back to Paris Hilton and not put it on the Web after all. But there reportedly are other copies out there. And yesterday, tabloid-news reports said there may also be a tape of a different Paris Hilton sexual encounter.

The series of events has become a titillating controversy-of-the-moment that the operators of Marvad say they would rather not deal with.

"They're the complete opposite of what people think a Web pornographer looks like," Blatt says of Marvad. "They've realized the mileage they've gotten out of the publicity. But these guys are very ethical, very honest about what they're doing. And for them it's not even about the porn. It's about the business."

The Web pornographers, in this case, are two 33-year-old longtime buddies, Roger G. Vadocz, who lives in Tampa, Fla., and Brian Marchlewicz of Seattle.

Information about the pair is limited to the words of their publicist and a few references on Internet sites devoted to pornography. They generally do a good job of staying out of the public eye.

Blatt describes Marchlewicz as the technical brains, while Vadocz has the looks and the marketing skills. They have made lots of money, Blatt says, without saying how much.

"They've done very well over the years," Blatt says.

In fact, he boasts, the pair are among the few tech-porn pioneers who have kept their ledgers in the black through the years. While others, including friends in the industry, were sued, prosecuted or bungled their way out of business, the pair stayed ahead of the game, says Blatt.