Donna Summer, who ruled the pop charts for years as a Bad Girl, is back on the road as a Good Girl, trying to prove that salvation can be as interesting as sin. Having burst on the scene in 1975 with the explicit sexuality of "Love to Love You Baby," Summer spent the next four years chasing singles up the charts -- "I Feel Love," "Bad Girls," "Hot Stuff," "The Last Dance," "On the Radio" and a duet with Barbara Streisand, "Enough Is Enough." The last song proved to be prophetic. Two years ago, Summer had a religious experience that has changed not only her life style but her approach to music.

"It was a necessary experience," Summer explains. "When I became successful, everything seemed to be too fast, too much. There was too little space for me . I had trouble relating to where I was at." Before 1975, Summer's career was mostly an overseas operation. After singing for a while in a Boston rock band, she went to Germany in 1968 and worked in musical theater: "Hair," "Godspell," "The Me Nobody Konws," "Porgy and Bess." She also worked with the Vienna Folk Opera and began her recording career with producers Giorgio Moroder and Pete Ballotte.

"After eight years of living in Germany, speaking a foreign language every day, I was living in America with people I din't know anything about," she says. The cultural shock was even greater, Summer explains, because "all of a sudden I was supposed to be either black or white; in Germany, I didn't have that sense of color, it was just me. So when I came back, I really had a sense of being lost, I didn't know who I was supposed to be."

The stunnign singer developed a "very heavy" dependence on prescribed sedatives, but eventually that "proved to be too much. I decided other things were important -- having a child, getting married, things we tend to shun in this modern day and age. I decided to align myself with the good things in life."

In late 1979, all of Summer's anxieties were released: She had an intense born-again experience, and she married musician Bruce Sudano; six months ago she gave birth to a girl, Brooke Lynn (named after her husband's band, Broklyn Dreams). "The only aspect of being born again that's bad for me is that I can't tell enough people about it," Summer insists.

The born-again experience, which has become more common for pop musicians in the last few years, has proved to be a creative pitfall for some artists (like Bob Dylan), but Summer is facing the situation headon and with practicality. Her last album, "The Wanderer," was certainly less overt than Dylan's recent efforts, containing a comfortable mix of pop, rock and gospel; "I Believe in Jesus" was even a hit on the pop charts. Summer says that radio programmers have not backed off from her music, but that concert audiences may have to bear with her a little bit.

"yi basically do all my songs, but I do them differently. I don't do them the way I used to do them and eventually I will cast them out," she says. "I have a commitment to fill and it would be unfair to people who are waiting to see a certain thing; that's what I did and unfortunately I'm stuck with doint it -- until I can get it to the point where it's changed, writing material that I don't mind doing, that's not an infringement on my new beliefs."

Summer's next album will be "spiritually inspired, but not conventioanl gospel." Since Summer is looking for a born-again producer, it will also mark a break with her longtime producers, Moroder and Bellotte. "One's an atheist and one's an agnostic," Summer sighs, "and since we're not on a basic level of sharing, it can be very hard."

Summer went to Germany in the late '60s because she was frustrated with the American music business, particularly its penchant for stereotyping. "Americans tend to do that. They could have greatness in front of their face and they wouldn't know it because they would be too busy looking at the packaging it came in. If I sent you a beautiful car in an aluminum cylinder, you'd say. 'I can't use that.' People can't get past the packaging. Look at Jimi Hendrix, the distance he had to go to get recognized."

Having finally shed the disco-doll and bad-girl image, Summer still has to hurdle the easy categorizations and comparisons that are made even as her artistic capabilities expand. "I'll always have that problem as long as my skin is black. Unfortunately people here will not categorize music for what it is. If I make a rock 'n' roll song, it could be better than anything, but because my skin is black, it won't get played." Actually, Summer's earliest professional experience was in an unsuccessful Janis Joplin-style rock band named Crow ("I was the only black member"), and she has spent most of the time since the erotic excess of "Love to Love You Baby" proving that she is much more than a manipulated sex kitten.

Manipulation is a major concern in Summer's life and art. She has a $10-million suit pending against Neil and Joyce Bogart, charging that she was "physically and emotionally ill when her cotnract was signed" with Bagart's Casablanca Records. (They have a huge countersuit against Summer charging breach of contract.) In a highly publicized move, Summer signed two years ago with David Geffen's new label. "My life, which was my career, was not my own," she says of the mid-'70s. "I couldn't even see my daughter [Mimi, 8, from an earlier marriage] and that really bothered me. But I don't hate anybody who's involved in this whole thing. It's business. It's the way things happen when parties can't resolve things."

Summer is full of energy right now. Her tour, which stops at Merriweather Post Pavilion tonight and tomorrow, is her first in more than a year. She had stopped working when she became pregnant, feeling it was "too personal to be jumping up and down on a stage." She's cautiously looking for film work, though she says "movies are very boring . . . and I hate to get up in the morning." Her first role, in the forgettable "Thank God It's Friday," was, she admits, "not something to write home about. I did the movie [so that Casablanca] could get 'The Last Dance' nominated for an Academy Award; they wrote in a little part so it wouldn't look like left field. I never took that seriously, though it was fun."

The movie situation is not dissimilar to Summer's problems with musical stereotyping. "I'd really like to play biblical movies or modern-day 'good' movies, something without a whole lot of rape and killing and dying and murder. I just can't handle that anymore." That, too, is a reflection of Summer's reinforced Christian values. "I never stopped being a Christian," she explains. "Being born-again is an affirmation that the person is going to make a personal effort to walk closer to God and bring Him into onel's life and start following His way. There are parts in your life where you can look back and laugh: 'I can't believe I did that; how could I have said that; where's my head at.'

"I'm sad that all the running I did was only running; it didn't get me anywhere. The spirit of rebellion in myself and in my songs would not let me rest. But I've chosen to stay in the world's eye, to give a positive image. It's a very spiritual and a very helpful place to be. I love it."