My S70 had an annoying rattle when I bought it too (~19,000 miles.) It turned out to be the glove box. Open the glove box door when you're on a bumpy road and have your passenger press on the bottom surface of the box - that isolated my car's rattle. The solution: remove the box (you don't have to removed the glove box door) and cram some packing foam around the glove box support. Hard to describe, but you'll see what I mean once you have the box out of the way. Volvo had the right idea - the box has foam tape in the problem area - they just didn't use enough foam. 12,000 miles later (on horrid Michigan roads) and my glove box is still silent...

Good luck and happy holidays!

Chelsea White