Williams had eight months out of the game with a knee injury after winning her second Wimbledon title and sixth Grand Slam title in 2003 and worryingly for her hopes of taking Olympic gold in August she injured the same knee in San Diego earlier this week.

This year has not been too kind to her either as she was beaten by fellow American Jennifer Capriati in this year's French Open before being sensationally trounced by 17-year-old Russian Maria Sharapova in the Wimbledon final.

But she says she has now got her priorities sorted out.

"I am determined to put all of my energy into tennis. I used to take things for granted before but now I hate to lose," she says.

It was at Wimbledon a year ago that her reign at the top of the game came to an abrupt end when she picked up a knee injury in the final.

Victory over elder sister Venus had given her a remarkable fourth Grand Slam triumph in five attempts before injury struck.

But she says watching the tape of the Sharapova defeat has made her hungry again.

"I didn't do anything I was planning on doing or had done in previous matches. I put so much pressure on myself. I couldn't relax before the match -- I'm a perfectionist."

Williams blames prolonged recovery from knee surgery and the murder of her half-sister, Yetunde, last year with draining concentration.

"No-one realises what I went through on and off the court," she says.

She hopes an Olympic gold medal will help get her back on track before the US Open in September.

And she is not yet ready to step away from the game.

"I'm nowhere finished with making history," she says.

She has not, however, abandoned hope of becoming a screen celebrity.

"There are few athletes who can make the transition from sports to acting," she says.

"I don't want to pontificate but I'm also in that group. I haven't seen many athletes who could be Oscar-winning actors."

Women's tennis has not been the same since the Williams sisters broke through.

Venus seem destined to rule but she has long ago been overtake by Serena, 23 in September.

"My sister and I changed the game, we brought in a new crowd, like Tiger Woods in golf," says Serena.

She played her first professional match in 1995 at 14 and made her tour debut in 1997 when in her second tournament in Chicago she beat former French and Australian Open champion Mary Pierce and former world No 1 Monica Seles.