Serena gets in the groove and shows no mercy in defence of her crown

Williams overcame a poor serving performance to advance to the third round with a 6-3 6-1 win over China's Meng Yuan on a day when world number one Justin Henin and 2006 Australian Open champion Amelie Mauresmo also advanced to the round of 32.

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Cut above: Serena Williams barely broke sweat in winning in Melbourne

But there were two big casualties, in 2004 Australian Open semi-finalist Patty Schnyder and France's number 13 seed Tatiana Golovin.

Schnyder, the Swiss number 15 seed, was beaten by Australia's Casey Dellacqua 4-6 7-5 8-6 - while Golovin went down to her compatriot Aravane Rezai 6-3 3-6 6-3.

Williams, the eight-time Grand Slam winner and three-time Australian Open champion, surprisingly had a first-serve percentage of just 51 against Yuan - yet it scarcely mattered.

Williams will now meet Belarus' Victoria Azarenka next, after the latter beat German Sandra Kloesel 6-1 6-1.

The number seven seed said: "It feels nothing like last year.

"It's so different - but I'm still enjoying every moment, like I was last year.

"I just want to win; I just want to fight - that's how I always am."

That is exactly what Williams will get in what seems an inevitable semi-final showdown with Henin, who is already eyeing her second Australian Open crown after beating Russia's Olga Poutchkova 6-1 7-5.

Henin will now meet Francesca Schiavone in the third round, after the Italian beat German Angelique Kerber 6-2 6-3.

Job done: Justine Henin celebrates her victory

The seven-time Grand Slam winner admitted that winning a second Australian Open crown to go with her 2004 success is a key ambition.

"I'd love to win every Grand Slam two times, so it means a lot to me," Henin said.

"Maybe Wimbledon means a little bit more to me - because it's the only one I have never won - but all Grand Slams are important to me."

Henin has already succeeded in part of her goal, having won the French Open in four of the past five years and the US Open twice.

The classy Belgian has had a chequered history at Melbourne Park, having controversially retired during the 2006 final against Mauresmo - while she missed 2005 through injury and last year following the break-up of her marriage.

Henin confirmed it is great to be back, after barely even watching last year's tournament on television.

"My mind was somewhere else," she said.

Master stroke: Justine Henin hits another winner

"I can tell you in January a year ago I really didn't miss my tennis at that time, because there were more important issues in my life.

"But maybe now a year later that it seems so far away from me, I can say I missed the tournament (last year)."

Meanwhile, Schnyder blamed the change in court surface at Melbourne Park for her failure to reach at least the fourth round of the Australian Open for the first time since 2002.

Schnyder said the change from the rubberised Rebound Ace surface to the newly-installed Plexicushion hard-court played a key role in her earlier than usual exit.

"It's a different court now," she said.

"It's very slow. The ball doesn't bounce as high and gets heavier, and it's very tough for me."

Dellacqua, who cut her ranking from 172 to 78 last year, will now meet Mauresmo in the third round.

Mauresmo, the number 18 seed this year following her injury-riddled 2007, needed 10 match points before finally subduing Russian Yaroslav Shvedova 6-4 7-6 (7/5).

Also advancing to the third round today were Czech number 12 seed Nicole Vaidisova, who ousted Australia's Alicia Molik in straight sets - while another Aussie, Jessica Moore, fell to Israel's Shahar Peer in straight sets.

Serbia's number three seed Jelena Jankovic also advanced in straight sets as she put her first-round scare behind her - while other winners on day three were France's Virginie Razzano, Russian Elena Vesnina and Japanese veteran Ai Sugiyama, who reached the third round for the first time since 2002.