The first new-look singles chart is due to be revealed - with "golden oldies" tipped to make a comeback.
Under new chart rules which came into force this week, any song available as an internet download is eligible for the chart regardless of when it was released.
Previously, songs could only be included if a physical copy of the single was also available in the shops. So Snow Patrol's Chasing Cars - released back in July - is expected to feature in this week's top 10.
Crazy by Gnarls Barkley, the monster hit of 2006, is likely to gain a top 40 placing, along with Maneater by Nelly Furtado.
Until now songs were automatically removed from the chart two weeks after the physical copy of the single was deleted.
The most surprising chart re-entry could be Mad World, the 2003 Christmas number one by Michael Andrews featuring Gary Jules.
The rule change means songs which appear in adverts or on film soundtracks are more likely to make a comeback.
Demand for downloads of Mad World have surged because it is currently appearing on a trailer for the Xbox computer game Gears of War.
The shake-up also raises the intriguing possibility of the Beatles staging an almighty chart comeback. There are rumours that EMI is negotiating to release the band's back catalogue as downloads for the first time.
HMV spokesman Gennaro Castaldo said: "If the Beatles' songs were made available digitally, there would be such a rush to download them that a top 10 made up entirely of their music would be almost guaranteed. "The chart will now offer a much broader representation of the nation's music tastes."
