here is one particular scene in Almost Famous that Cameron Crowe still cannot watch without feeling pangs of embarrassment and nostalgia. There he is, a wide-eyed 15-year-old, losing his virginity in a hotel room to a trio of voracious groupies while the girl he really fancies leaves the room.   "It's agonizingly true," he admits. "I was too young to really understand what was going on, and what I most remember is that the girl I really wanted to stay in the room left me with her friends - the B team."   Crowe, portrayed in the film by newcomer Patrick Fugit, was deflowered by the groupies while he was a young journalist covering a rock band's American tour for Rolling Stone magazine.   "The girls were kind of like a carousel going around me and it's never happened anywhere close to that way since then," he says. "It was my first time and I figured if I don't put that in the movie I am not disclosing everything. More than the sexual escapade, there was a real ache in that the girl I felt most for waved, said goodbye and left."   Writer-director Crowe has poured his experiences and memories into Almost Famous, an intensely personal story focusing on his turbulent family life and his early days on the road with rock bands that included Led Zeppelin, the Allman Brothers, the Who and the Eagles.   The girl he wanted but could never have is named Penny Lane in the film and is portrayed by Kate Hudson. She was a devoted groupie - the girls are called "Band Aids" in the film - and was in love with a famous rock guitarist until, fed up with her, he broke her heart by selling her to the British band Humble Pie for $50 and a case of Heineken.   "It all happened and I think it's good that I'm slightly embarrassed about it because if I'm not, I'm probably not telling the total truth," says 43-year-old Crowe, who was Oscar nominated in 1996 for his Jerry Maguire.   He has stayed in touch with the Penny Lane character over the years and he telephoned her when he was making Almost Famous. "We brought her to Los Angeles and I showed her the movie recently and after she went home she wrote me a letter saying that if she died tomorrow she would be satisfied there was a film that described what it was like to love music and dedicate your life to it."   Although Stillwater, the rock band in the film, is a composite of several bands, the singer, played by Jason Lee, and guitarist Russell Hammond, played by Billy Crudup, are strongly reminiscent of Led Zeppelin lead singer Robert Plant and guitarist Jimmy Page.   Zeppelin also gave Crowe permission to use five of its songs in the film after Crowe flew to London and screened it for Page and Plant. Crowe and his wife, Nancy Wilson of Heart, co-wrote five more songs for the film.   As a fly on the wall, Cameron Crowe was both a friend and chronicler of the rock stars of the '70s - a privileged position which had its drawbacks when it came to some of the wilder excesses.   In one scene, after he spends three weeks on the road with Stillwater, the young journalist turns in his article to Rolling Stone. The magazine's researchers call Billy Crudup's character to check the facts and he denies everything the kid has written.   "That happened with Neil Young, who was an artist I really admired," recalls Crowe. "I spent a couple of weeks on the road with him and turned the story in. The fact checkers called him, and he said it wasn't true and he had never said it was okay to do the story.   "I felt like I'd been hung out to dry and betrayed by a guy I cared a lot about. I called Neil Young's manager and said I was in trouble and I was going to get fired. So Neil Young changed his mind at the last minute and called Rolling Stone to say it all happened and he didn't want me fired."   For Crowe, the '70s were the best years for covering the exploits of rock bands. "The world was a little smaller then and you could be part of this travelling cocoon of a rock band on the road. You were inside looking out," he says.   "I met all these vivid, very passionate people that had this great love of music, and that's what I wanted to capture in the movie." - Rebecca Carnforth