Big shake-up
Lewis, who won the ITV show the X Factor, has now been at number one for three weeks with her single A Moment Like This.
The highest new entry comes from Eric Prydz, whose remix of the Pink Floyd classic Another Brick In The Wall enters the chart at number two.
There are also new hits for U2 and JoJo - whose single, Too Little Too Late, would not have been eligible for the chart until next week under the previous rules.
Snow Patrol's album, Eyes Open which is in its 36th week of release, continues to ride high in the charts at number three.
The new chart rules have been hailed as the biggest shake-up in the chart since its inception in 1952, and could mean old favourites might make their way back into the charts.
Until now downloads only counted towards chart positions if they were purchased within a week of the physical single being released and two weeks of it being deleted. But this week's Top 40 sees several deleted songs re-entering the chart, including Crazy by Gnarls Barkley which was the biggest selling single of 2006, and is now at number 30.
Broader representation
Nelly Furtado's Maneater also re-appears at number 38 after originally making number one in June last year.
Outside the top 40, four songs from the High School Musical soundtrack have entered the chart - including two that were previously considered album tracks.
Michael Andrews and Gary Jules' single Mad World, the Christmas number one in 2003, is another re-entry at number 58.
The song, which featured in the cult movie Donnie Darko and can currently be heard in the advert for Xbox 360 game Gears of War, made its last chart appearance April 2004.
Industry experts believe the charts will never be the same again because downloads will change the pattern of how tracks climb.
"Under the new rules, anything and everything is eligible," said HMV spokesman Gennaro Castaldo.
"The charts will now offer a much broader representation of the nation's music tastes," he added.
It is rumoured EMI is considering releasing The Beatles' back catalogue as downloads for the first time.
Castaldo thinks if that happens then a "top 10 made up entirely of their music would be almost guaranteed".
