ASHTON Kutcher may have a very impressive Hollywood career already, but there's no denying he's more famous for his romance with Demi Moore than for his acting.

Despite roles in films like Cheaper By The Dozen and Just Married, with former girlfriend Brittany Murphy, his relationship with Demi, who is 16 years his senior, has catapulted him out of relative obscurity.

Now the lanky former Iowa country boy wants to prove he can act as well. Unfortunately the 26-year-old's acting career to date has mostly been in dumbed-down comedies like Dude, Where's My Car?

That's why Ashton hopes his starring role in the time-swapping psychological thriller The Butterfly Effect, which opens this week will prove that he's so much more than just a pretty face.

It's a complicated drama about a troubled man who suffers a psychological disorder that allows him to go back and make decisions that change how things turn out.

Dabbling in child abuse, it's a disturbing film and Kutcher was a surprising choice for such a mind-twister.

"If anything, I'm a trier," says Kutcher about his eyebrow-raising casting. "It was certainly a deliberate choice to do something new. This was a dramatic movie in which I appreciated the character, the metaphors of this story and the message."

It was a big leap from doing the television series That 70s Show and the youth-orientated comedies he's used as his springboard, admits Ashton.

"This character was pretty disturbed and what was really tough was that in order for me to be confident when the cameras started rolling, I had to stay really focused on what we were doing."

A nine million dollar film shot in Canada, Ashton says he liked the theme about going back and changing the past.

"This character blocks out all the traumatic moments in his life as we as a society tend to do all the time. Getting the base character was probably the toughest part. I had to establish someone people would go, 'OK, he is the same guy that he was, but this is a different version of him'."

The film's writers and co-directors J Mackye Gruber and Eric Bress admit they had serious initial doubts about Kutcher's lightweight screen image.

"Honestly, when his name was first suggested, we were both like, 'No way is he in this movie!'."

That's where the public image of Kutcher may be unfair, he studied biochemical engineering at university, before dropping out to pursue a modelling career, and has developed his own updated Candid Camera TV series Punk'd.

In the pipeline is a possible remake of Guess Who's Coming to Dinner?

All the media fascination with his tabloid-hot love life makes the casting of the former male model now seem like a stroke of luck. Being Demi's toy boy has done wonders for his name recognition.

But there was nothing calculated about it, says Ashton.

"I don't wake up in the morning and go, 'Wow, I'm a desirable hot guy'. I came into the world with what I've got and this is the shell that I'm living in. I can only be grateful for what I have."

He harks back to The Butterfly Effect when talking about the effect Demi has had on his life. "The lesson I've learned is that every action you make counts, somebody's watching, somebody's making a judgement. Which I think ironically is the lesson of this movie."

Demi, who has three daughters with former husband Bruce Willis, is an old hand at handling the media spotlight, he says.

"She's very crafty, there's a reason why she hasn't been living in Los Angeles for the past five years. She's good at it, it just kind of becomes part of your day and you keep doing what you're doing."

Ashton says there's no training that can prepare you for major fame. "There's not a handbook you know, I don't have the slightest idea. I know what the truth is and I don't care what they write about me."

All this media fuss didn't start when he began dating Demi, he maintains. Ashton already had a dating record that included actresses Brittany Murphy and Ashley Scott.

"I started acting five years ago, I was on the cover of Rolling Stone before I ever met Demi, I have a television show that's watched by millions of people. All of this kind of hit at the same time.

"I work a lot and was doing very well before I ever met her," he adds. "So I don't think it's all about who I'm dating."

He didn't even know who she was when they first met, he smiles. "The first time I ever saw her I didn't know who she was. I sat and talked to her not having the slightest idea I was talking to a famous person."

Having done a film about changing the past to effect the present, would he change anything in his own past?

"I've had relationships that have fallen apart in my life and it's my job to mend those," he says.

"It's about changing yourself so you can change who you are. We don't have to go through time travel to do that."