She swamped Petrova, 6-1, 6-2, smacking 19 winners and committing only six unforced rally errors in a match many thought she could lose.
Williams wasn't smirking after this third-round victory, but there was a self-satisfied smile on her face.
"I don't think it was any of her fault," Williams said. "I just had a really good day out there. I just had all the right shots."
The heavy-hitting Petrova was out-muscled in the longer skirmishes and definitely out-served. Not only did Williams average 85 mph on her second serve, up a good 10 mph over some key losses in 2002, but she had only one double-fault.
If Williams puts on the same sort of display in the round of 16 against Vera Zvonareva, who beat her at the French Open, all doubts about her motivation will be erased.
Zvonareva, the No. 16 seeded Russian who continues to ascend toward the top 10, rolled past Iroda Tulyaganova, 6-3, 7-5. She hasn't lost a set.
Six other players in the bottom half of the draw made the round of 16: No. 2 Kim Clijsters, No. 5 Lindsay Davenport, No. 13 Ai Sugiyama, No. 27 Silvia Farina Elia and unseeded Shinobu Asagoe and Paola Suarez.
Elia upset seventh-seeded Chanda Rubin, who won Eastbourne last Saturday, 7-6 (6), 6-3. Rubin fought off four match points. Rubin was considered a long shot to win Wimbledon, but was definitely among the top five or six prospects.
The women will complete the round of 16 today with top-seeded defending champion Serena Williams heading the card against No. 28 Laura Granville of Chicago.
How long it has been since Venus' play looked this sweet against a top opponent and this is the sort of high she needs going into the Zvonareva rematch.
The Zvonareva rematch, she insisted, "will be a lot different. It's nice for her to have the win at the French. Obviously, it wasn't nice for me. Even if I had won that match, I don't see where I would have been able to do very much at the French, to be honest. I tried to do what I could do, but I just wasn't ready."
Williams, the No. 4 seed, had little practice going to Paris because of an abdominal muscle pull, which is now virtually cured. It was evident in the days before Wimbledon, as she practiced, that she was hitting her serve full out and yesterday she was rocking it.
A win in the fourth round would mean a probable showdown in the quarters with Davenport, who has gotten progressively stronger here. After a shaky first-round win over wild card Samantha Stosur of Australia, Davenport has breezed past Rita Grande and now Cara Black. Best of all, she has had no recurrence of the nerve problem in her left foot.
"When it was bad at the French Open, I had a hard time putting pressure on it," Davenport said. "For the time being, though, that's cleared up and I really feel I can use both my feet and push off a little bit easier."
Davenport said there was a constant buzz in the locker room before the Petrova-Williams match. Most were expected it to be close, but not Davenport.
"I thought Venus would dominate because she would be fired up, be ready," Davenport said.
Charles Bricker is a reporter for the South Florida Sun-Sentinel, a Tribune Publishing newspaper.
Sjeng Schalken (8), Netherlands, def. Victor Hanescu, Romania, 6-2, 6-4, 7-6 (3).
Paradorn Srichaphan (12), Thailand, def. Rafael Nadal, Spain, 6-4, 6-4, 6-2.
Andy Roddick (5), United States, def. Tommy Robredo (25), Spain, 7-6 (5), 6-4, 6-4.
Rainer Schuettler (9), Germany, def. Todd Martin, United States, 4-6, 7-5, 6-7 (1), 6-1, 7-5.
Jonas Bjorkman, Sweden, def. Justin Gimelstob, United States, 6-1, 6-3, 6-3.
Max Mirnyi, Belarus, def. Ivo Karlovic, Croatia, 7-6 (5), 3-6, 6-3, 7-6 (4).
Roger Federer (4), Switzerland, def. Mardy Fish, United States, 6-3, 6-1, 4-6, 6-1.
Feliciano Lopez, Spain, def. Flavio Saretta, Brazil, 6-4, 6-4, 6-4.
Vera Zvonareva (16), Russia, def. Iroda Tulyaganova, Uzbekistan, 6-3, 7-5.
Ai Sugiyama (13), Japan, def. Nathalie Dechy (22), France, 6-4, 6-4.
Venus Williams (4), United States, def. Nadia Petrova (29), Russia, 6-1, 6-2.
Kim Clijsters (2), Belgium, def. Samantha Reeves, United States, 6-1, 6-2.
Lindsay Davenport (5), United States, def. Cara Black, Zimbabwe, 6-2, 6-2.
Shinobu Asagoe, Japan, def. Francesca Schiavone, Italy, 7-5, 6-2.
Paola Suarez, Argentina, def. Maja Matevzic, Slovenia, 5-7, 6-3, 7-5.
Silvia Farina Elia (27), Italy, def. Chanda Rubin (7), United States, 7-6 (6), 6-3.