When it comes to country love songs, it's hard to top Dolly Parton's heartfelt "I Will Always Love You." Indeed, the bittersweet ballad grabbed the peak position on a new special, CMT 40 Greatest Love Songs, which premiered Saturday (Feb. 12).

During her interview for the special, Parton said, "Of course, 'I Will Always Love You' is the biggest song so far in my career. I'm famous for several, but that one has been recorded by more people and made me more money, I think, than all of them. But that song did come from a true and deep place in my heart."

Parton was attempting to make a break from her role on Porter Wagoner's syndicated television show at the time she wrote the song.

"I was trying to get away on my own because I had promised to stay with Porter's show for five years. I had been there for seven," she said. "And we fought a lot. We were very much alike. We were both stubborn. We both believed that we knew what was best for us. Well, he believed he knew what was best for me, too, and I believed that I knew more what was best for me at that time. So, needless to say, there was a lot of grief and heartache there, and he just wasn't listening to my reasoning for my going."

She continued, "I thought, 'He's never going to listen. He's just going to bitch every day that I go in to talk about this.' So I thought, 'Well, why don't you do what you do best? Why don't you just write this song?' Because I knew at that time I was going to go, no matter what. So I went home and out of a very emotional place in me at that time, I wrote the song, 'I Will Always Love You.'"

Even though she was determined to move on, Parton especially wanted to convey a message of gratitude in the song.

"It's saying, 'Just because I'm going don't mean I won't love you. I appreciate you and I hope you do great and I appreciate everything you've done, but I'm out of here,'" she explained. [That's] basically what I was saying. And I took it in the next morning. I said, 'Sit down, Porter. I've written this song, and I want you to hear it.' So I did sing it. And he was crying. He said, 'That's the prettiest song I ever heard. And you can go, providing I get to produce that record.' And he did, and the rest is history."

The song climbed to No. 1 on the country chart in 1974. Eight years later, a new version she recorded for her film, The Best Little Whorehouse in Texas, peaked atop that chart, too. However, the soaring ballad exploded at pop radio when Whitney Houston sang it in The Bodyguard, the 1992 movie produced by Kevin Costner, who also starred opposite Houston.

"Kevin Costner and his secretary are the ones that loved the song," Parton said. "They had another song that was going to go in that place, and someone had recorded the song they were going to use. They were just in a panic at the last minute. And so they asked me about the song. I sent it. I didn't hear anything more."

In time, Parton heard Houston's version on her car radio -- "and about had a fit," she said.

"They started out with it a cappella, and I thought, 'That sounds familiar -- "If I should stay ... ."' And it didn't hit me. It was just one of those things where [you think], 'What is that?' And, then all the sudden, when she started singing, 'I will always love you,' I just about wrecked the car," Parton said.

Houston's dramatic rendition moved more than 4 million singles and won two Grammys. Meanwhile, The Bodyguard soundtrack sold a staggering 17 million copies.

"The effect that it had on the whole world was amazing," Parton said. "It's been one of the biggest songs ever."