No. 2 Williams conquered No. 13 Magdalena Maleeva of Bulgaria, 6-0, 6-3, on Sunday (Saturday in the United States), while third seed Hingis demolished 15th seed Amanda Coetzer of South Africa, 6-1, 6-0, in the fourth round of the Grand Slam event.

In the topsy-turvy men's draw, Tim Henman of Britain became the latest high men's seed to crash out of the tournament at Melbourne Park.

Williams drove over the potential roadblock posed by Maleeva. Known for dominating most of her opponents, the American had lost two of her three meetings with Maleeva, including a straight-sets ouster at last year's Nice Indoor event.

The reigning Wimbledon and U.S. Open champion, Williams showed no signs of the struggles she experienced on Friday. The 21-year-old slipped by No. 32 Daniela Hantuchova of Slovakia, despite suffering with tendinitis in her left knee.

Meanwhile, three-time champion Hingis displayed supreme confidence at Rod Laver Arena. The Swiss star beat Coetzer for the eighth time in their 10 career meetings. Hingis, in fact, has dropped just five games in their last two meetings.

Next, Hingis will encounter surprise quarterfinalist Adriana Serra Zanetti. The Italian recorded 20 winners on the way to a 6-1, 7-5 victory over Slovakia's Martina Sucha.

Serra Zanetti, 25, reached just her fourth career quarterfinal on the WTA Tour and first since the 1999 Sao Paolo event.

Williams faces a far more experienced quarterfinal opponent -- four-time champion Monica Seles of the United States.

No. 8 Seles was ahead in the fourth set, 4-2, when Spanish teenager Ana Isabel Medina Garrigues retired from their fourth-round match due to a knee injury.

The 28-year-old American advanced to the quarterfinals for the seventh time in as many appearances here. She also extended her WTA Tour winning streak to 17 matches.

Medina Garrigues, who was competing in the fourth round of a Grand Slam event for the first time, sustained the injury when she fell to the court on the final point of the sixth game.

Despite receiving treatment from a trainer, Medina Garrigues only managed to make it through the first two points of the next game before throwing in the towel.

On the men's side, Jonas Bjorkman had seven aces and 47 winners as the unseeded Swede overpowered No. 6 Henman, 6-2, 7-6 (8-6), 6-4, in the fourth round.

The top five seeds failed to advance past the second round here, marking the first time that has occured in a Grand Slam event in the Open Era.

Henman also failed to reach his first Grand Slam quarterfinal outside of his own country.

A three-time Wimbledon semifinalist, Henman stumbled in the fourth round at Melbourne Park for the third straight year. He has reached the fourth round of the U.S. Open twice, but never moved past the third round of the French Open.

Bjorkman improved his career record against Henman to 5-2.

A semifinalist at the 1997 U.S. Open, Bjorkman also knocked off seeded foes in the previous two rounds -- No. 24 Thomas Enqvist of Sweden in the second round and No. 12 Guillermo Canas in the third.

Prior to this tournament, Bjorkman had conquered a seeded player at the Australian Open just once in eight attempts.

No. 26 Jiri Novak of the Czech Republic will meet Stefan Koubek of Austria in the quarterfinals.

Novak overcame Slovakia's Dominik Hrbaty, 6-4, 6-2, 5-7, 6-2, winning for just the second time in six all-time meetings with Hrbaty.

Koubek outdueled Chilean qualifier Fernando Gonzalez, 7-5, 6-1, 6-7 (3-7), 6-2.

Looking to set up an all-Swedish quarterfinal, No. 16 Thomas Johansson meets unseeded Adrian Voiea, who will attempt to become the first Romanian to make the last eight here.

Both players have reached the fourth round of the Australian Open for the first time.

Johannson achieved a career-high ATP ranking of 14 last year after winning consecutive grasscourt titles at Halle and Nottingham.

Voinea won back-to-back five-set matches against Frenchman Julien Boutter and American Taylor Dent to advance to the last 16.