Is the download you're looking for no longer available? :( Free-and-legal tracks are often offered only temporarily, so I'm sorry if you have missed the window for this one. Look to the right to subscribe via email, feed reader, blogloving, twitter, etc, and I'll make sure that you never miss out on free music again!
You can find a free download of a new version of Trans-Siberian Orchestra's track "Dream Child" available on Amazon right now. This one is much more of a melodic ballad then the rock/orchestral mash-ups that the Trans-Siberian Orchestra is generally known for, but it is a very pleasant, dreamy piece.
If you like instrumental electronic rock Christmas music in general, you might want to check out Mannheim Steamroller -- unfortunately not free, but definitely my favorite for that style.
There's a veritable bonanza of free holiday music available this Christmas season! Take a peek at the rest of my findings so far, and check back every day for more!