Princess Diana is a little passé at the moment. There's nothing more dated than the celebrity of a decade ago. We've moved on to other concerns, and the celebrity's look, once so fresh and startling, has become as stale as an old TV show. But in the long run I don't worry about Diana. She's one of the century's greats, right up there with Elvis and Marilyn. She may even turn out to be the greatest one of all. Five thousand years from now there will be folk tales about her, like Guinevere and Helen of Troy.

That is the reason you won't want to miss the exhibit about her that's on view at St. Pete's Florida International Museum Feb. 19-June 12. (I saw the show in Fort Lauderdale earlier.) It consists mainly of artifacts from her life, selected by her brother. I'm sure you remember him from the funeral, when he delivered that sensational eulogy chiding the royal family. Well, he's now turned into the Earl You Love to Hate, causing trouble and making mercenary decisions about his sister's estate.

Luckily, the exhibit turns out to be one of his better ideas. It's all about the Spencer side of Diana. This an excellent way to tell her story, it turns out; whatever else she was in her bizarre life, she was always a Spencer girl. The kind of things you would want to show people about your own dead sister-her toys, her childish drawings, her ballet shoes-they're all here. They give the exhibit the ring of truth. You feel that a real person is being evoked.

She was a sweet but ordinary child with a cat named Marmalade and a minor talent for dancing. Her parents were divorced and she was often away at school, where she fit in rather well. She was no student, though. Her report cards show teachers grasping for something nice to say; so many comments are "much improved" that you can only wonder how bad she was to begin with. Once she is chided for not always using capital letters when necessary, to which I say, how could they tell? I find her handwriting maddeningly difficult to decipher, even more of a shame because she wrote such interesting things.

Take her diary from 1979, for instance. It's open to a page for a week in August, when two very important things happened- Lord Mountbatten was assassinated and she was a guest of the Queen's at Balmoral. Historians record that her displays of sympathy in Prince Charles' presence did much to direct his emotional interest toward her.

Maybe it's my imagination, but I found much more going on between the lines. In her jottings about social engagements and whom she glimpsed ("saw Princess Anne on a walk, waved as she passed") I saw the climbing, ambitious side of Diana. She clearly was a little in awe of the royal family and wanted their acceptance and social validation. Of course, that's only my interpretation, due in part to the hard-to-read handwriting. There was another entry that seemed to say, "Princess Margaret is drunk," although I'm sure it's something more like, "Princess Margaret came by for a drink."

At any rate, after losing yourself in the Princess's childhood you turn a corner and there's her wedding dress. In person it's like encountering Mount Rushmore-you've seen its picture so many times that the original is sort of a letdown, although the 25-foot train is impressive. It looks like a little girl's idea of a wedding dress, or perhaps Walt Disney's. I personally found the shoes, which you never get to see, much more interesting.

Up until this moment you're still sitting on the fence about the exhibit. The pickings have been kind of slim, and at almost $20 admission you feel a little foolish for lining the pockets of Charles Spencer. Then you turn a corner and there are the clothes. You gasp. You realize you are not just getting your money's worth. It would be cheap at twice the price.

There are about 30 or so outfits, the perfect number for comfortable viewing, and they are draped on mannequins, obviously, the same size and shape as the Princess. The effect is that of a room full of "ghost Dianas." She wore these things. Little "Diana rays" are emanating from them. You can almost smell her perfume.

The collection is brilliantly chosen to show the nuances of the Diana style. In the beginning, when she was just entering into her public life, the gowns are simultaneously girlish and dowdy, rather like the wedding dress. She was only 20 years old, of course, and not yet the icon she became. But after a year or so she picked up the pace, appearing in those suits we know so well (usually monochromatic and simply cut, with an enormous matching hat), and in evening gowns that became increasingly simple and sophisticated.

During her royal tenure it was her job to showcase the British fashion industry, such as it is, and she did a wonderful job. But after her divorce she didn't have to worry about such things, and began to patronize the greatest designers in the world. Here she blossomed to her full potential. Princess Diana and Versace were quite a combination. Any thoughts you might have about Gianni being too wild or vulgar or too Jennifer Lopez are dispelled when you see the trio of gowns he designed for the Princess. They are simplicity itself, columns of color, glorifying Diana's remarkable body with its broad shoulders and long, long legs so that it becomes the very essence of feminine perfection.

After the clothes comes the funeral. It features three different versions of Charles Spencer's famous speech, which seemed so remarkable at the time but now comes across as not very gracious and more than a little self-serving. The dramatic subplot of Diana's last days is not dealt with, and that is just as well. I'm told that in the Middle East it's taken as fact that Diana was murdered on the Queen's orders because the Princess was either about to marry Dodi Fayed, a Moslem, or was pregnant by the Pakistani doctor, also a Moslem. Or both. How appropriate that her mysterious death should fall at the nexus of the world's current crisis.

My own favorite image of the Princess-not in the exhibit-was taken as she strode out of the back door of the Ritz and into that Mercedes on the night she died. It's not the ghoulish or emotional aspects that attract me to the picture. It is, quite frankly, the clothes. She is wearing white stretch slacks that end hugging the top of her ankle, stiletto sling-back shoes, a black silk T-shirt and a midnight blue blazer. On one wrist is a Rolex, on the other a bracelet from Cartier. She's tanned from her Riviera vacation and her blond hair is short and brushed back. She is caught in mid-stride, her famous legs shown off to their best advantage, as she races toward her destiny and the millennium races to its close.

For more information about Diana: A Celebration, call the Florida International Museum at (727) 822-3693, or go to floridamuseum.org.