It's the Lacrimosa section from Mozart's Requiem Mass.
Mozart's Requiem.
It's beautiful.
Mozart's Requiem in D minor (Lacrimosa)
Which Commercial?
Cannon by Pachelbel.
The background music has no known name. It was commissioned for the tamiflu ad and produced by facethemusic.com
Flight of the Bumblebees
a version of ride of the Valkyries
Bach
the singer in the background is Enya
poisoned well
ladies and gentlemen - saliva
Pachelbel's Canon.
Most music for commercials is specially composed for each situation. It may sound similar to something familiar, but may not be exactly the same due to copyrights, performer royalties and the like.
Sweet Disposition by The Temper Trap.