Todd White scored the go-ahead goal with 8:55 left in the second period and Radek Bonk tallied twice as the Senators advanced to the Eastern Conference semifinals with a 4-1 victory over the Islanders.
Patrick Lalime recorded 31 saves for the Senators, who won four straight after losing the series opener. Ottawa allowed only four goals following a 3-0 loss in Game One.
"We knew what we did wrong in Game One and we didn't want it to happen again," Lalime said. "Penalty killing was a big factor in this series. We expected a good effort from them playing desperate hockey. Scoring the first goal was a key."
The Senators advanced to the conference semifinals for the second straight year and the third time in franchise history. They have never been beyond the second round of the playoffs.
"It was good to win it at home," White said. "We'll have a week to prepare for the next team."
Daniel Alfredsson, the Senators' second-leading scorer in the regular season, was held without a goal in the series, but played a key part in the clincher.
Alfredsson stole the puck along the right boards following a dump-in and passed to Wade Redden just inside the left blue line. Garth Snow made a kick save on Redden's slap shot, but White swept in the rebound with traffic in front, giving the Senators a 2-1 lead.
"Alfie made a great play back checking with me and then made a great pass to Redden," White said. "He got a good low shot and the rebound came to me. I tried to get it upstairs and fortunately I did."
Martin Havlat, who scored Ottawa's first goal, set up Bonk's insurance tally with another spectacular individual effort. Havlat intercepted Snow's clearing attempt along the boards, skated around defenseman Radek Martinek and passed in front to Bonk, who tipped a one-timer past Snow with 1:47 left in the second period.
Bonk capped the scoring with an empty-net goal with 2:15 remaining. The Islanders pulled Snow 15 seconds earlier for an extra skater.
"We seem to be playing with more confidence and tonight was right from the beginning," Senators right wing Marian Hossa said. "After Game One, our role players held their heads and were determined to come out stronger. We found a way to win tonight because everybody had energy and jump."
Havlat gave the Senators a 1-0 lead when his centering pass deflected in off the skate of New York's Shawn Bates for a power-play goal with 6:07 left in the first period.
"Some big hits early and scoring on the power play got us rolling and them we played a solid game from there on," Alfredsson said. "We wanted to play smart and play deep behind their defense."
Dave Scatchard drew two straight penalties in the second period and the Islanders converted the 5-on-3, drawing even when Mark Parrish banged in Alexei Yashin's rebound at 6:48. But the tie lasted just over four minutes.
New York was ousted in the first round for the second straight year. Last season, the Islanders fell to Toronto in seven games.
"I thought we were on our way when we scored on the 5-on-3," New York captain Michael Peca said. "We wanted to keep close defensively, have aggressive forechecking and control the neutral zone."
New York coach Peter Laviolette predicted a victory for his team, but the Islanders simply could not generate enough offense in the series against the defensive-minded Senators.
"The overtime loss (in Game Three) in New York kind of gave them control," Yashin said. "I feel we played some good games, but we just couldn't get any goals."
New York outshot Ottawa, 13-4, in the third period, but failed to cash in three power plays. The Islanders finished 1-for-5 with the man advantage and dropped to 22-3 when winning the opening game of a series.
"The key was in New York, when they only used three lines and four defenseman," Havlat said. "They were tired and then they played back-to-back games. It's a good break, a week without a game. It'll be nice to rest and get ready for the next round."
Snow finished with 15 saves for New York.
"When it comes to the end of the season, you try to validate your year and try to learn from the experience," Snow said. "What we did was obviously not good enough."