How does it all work with DLC from XBL?

[Girth]

I've not downloaded any DLC for specific games yet, but I was just wodnerng how that works? As in - if I wanted to buy a guitar hero song for instance, could I still do that, yet play it with a backup game disc? Or howabout the new Burnout Paradise DL stuff?

[Acheron]

You can indeed.

[Girth]

cool - cheers.
:)

[Girth]

Ok, so I d/l the Burnout Paradise bikes pack, but the game simply doesn't see it. I've looked on line and people say that the bikes should just appear in the list, bt they don't. Have I done something wrong then?