Dolly Parton was listening to her car radio the first time she heard Whitney Houston's version of "I Will Always Love You," a song actor and film producer Kevin Costner insisted she record for the 1992 film, The Bodyguard.

"They started out with it a cappella," Parton said in 2011 when the bittersweet ballad grabbed the peak position on the CMT 40 Greatest Love Songs special. "And I thought, 'That sounds familiar. ... 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's country hit became a signature song for Houston, who died Saturday (Feb. 11) in Los Angeles at age 48.

Houston's dramatic rendition of "I Will Always Love You" sold more than 4 million singles and won two Grammys. The Bodyguard soundtrack sold 17 million copies.

Parton wrote the song while attempting to make a break from her role on Porter Wagoner's syndicated television show. 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 in the Love Songs interview. "[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."

Parton's original recording reached No. 1 on Billboard's country songs chart in 1974. The song topped the chart again in 1982 when she re-recorded it for the film, The Best Little Whorehouse in Texas.

It became a hit yet again when Houston recorded it for The Bodyguard, a film Costner produced and co-starred in.

"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 a 2008 interview with CMT.com, Costner said he didn't detect any great enthusiasm when he insisted that Houston sing Parton's composition. Among those responding were Arista Records chief Clive Davis and the other executives from Houston's label.

"When I said to Whitney, 'You're gonna sing "I Will Always Love You,"' the ground shook," Costner said. "Clive Davis and those guys were going, 'What?!'

"I said, 'This is a very important song in this movie.' I didn't care if it was ever on the radio. I didn't care. I said, 'We're also going to do this a cappella at the beginning. I need it to be a cappella because it shows a measure of how much she digs this guy -- that she sings without music.'"

Parton has always praised Houston's version of the song, noting, "I will always be grateful and in awe of the wonderful performance." She has also expressed her gratitude to Costner for including the song in The Bodyguard.

"She said something to me off the record, so I won't ever repeat it, but it was so beautiful, and it was so Dolly," Costner said. "It was generous and it was funny -- everything that she is -- but it was a big thank you. It was a big, fat thank you."