Paris Hilton gave herself an extra-special birthday treat this year - a videotaped sex romp with her best friend, a Playboy Playmate, sources told The New York Post.

Not only has Hilton appeared in at least 10 amateur pornographic flicks, the horny hotel heiress also filmed a tryst with Playmate Nicole Lenz, a Frederick's of Hollywood model, on Feb. 15, 2003 - Hilton's 22nd birthday, sources said.

Three sources told The Post they've seen the steamy girl-on-girl video, which took place at the Bellagio in Las Vegas on a camera Hilton owned.

They described it as "graphic" and said it also involves a Hollywood actor.

"Jason [Shaw, Paris's then-boyfriend of two years] had just broken up with her," a pal of Shaw's said.

Hilton's friend added: "Paris was partying pretty hard at her party at [Las Vegas club] Light and then filmed the video later that night in her room at the Bellagio."

After filming, Shaw went to Hilton's Hollywood home to clean out his belongings and "found a video of Paris having a tryst with Nicole," Shaw's pal added.

A business acquaintance of Shaw's - who owns several clubs in L.A. that Shaw invested in - heard of the tape and started shopping it around without his knowledge, Shaw's friend said.

One person in the skin trade, who saw the tape in March 2003, said:

"I saw the tape but [the friend of Shaw's] wanted $1 million. I passed."

Another company, "Girls Gone Wild," released a statement when asked specifically about the tape of Hilton and Lenz.

" 'Girls Gone Wild' was indeed approached about a Paris videotape. We would have absolutely nothing to do with an improperly attained video and told the person approaching us such," the statement said.

Once Shaw found out his pal was shopping the tape without his consent, he destroyed it, a source said.

"Jason is furious about this," the Shaw pal added. "He broke up with Paris because he didn't want to lead that kind of life. He is a great guy, from a good family. He didn't ask for the tape nor did he have anything to do with it. It was thrust upon him. He watched it and then destroyed it."

Shaw told The Post: "I dated Paris for a little under two years. Our relationship ended in early 2003. We are still good friends, and I hold her in high regard. After our relationship ended, I became aware of the existence of a private tape which involved Paris. I destroyed the tape. I never offered to sell the tape nor did I ask or agree for anyone else to sell it."

But one source says Hilton may still have her copy and claims to have seen it recently, within the past few months.

"Paris showed me the [tape with Lenz] and then asked me to help her get back the Rick Solomon tape," the source said.

A rep for Hilton declined comment. Lenz did not return calls.

Meanwhile, Don Thrasher, the man who sold the Hilton/Rick Solomon tape to Internet pornographer Roger Vadocz, told "Celebrity Justice" he received $50,000 for the tape - and gave half of that amount to Solomon in cash.

He also told the entertainment news show Solomon detailed ways of shopping around the sex video.

Solomon's lawyer, Marty Singer, insists his client had nothing to do with the sale of the tape and claims Thrasher secretly took it from Solomon's home, duplicated it and returned it.

An exhausted Hilton, just off a flight from Australia yesterday, refused to answer questions about her numerous raunchy tapes, but did muster enough energy to plug her Fox TV show, "The Simple Life."

"I just want to go home to my family right now," she told The Post at Los Angeles International Airport.