The DSP module is located in the left hand side of the trunk, under the shelf that hold the MK and CDC. It is the big black box at the bottom. You will have to remove some other plastic pieces in that area to get access to the bolts, in addition to the shelf area cover.

This might help:

http://www.xoutpost.com/classifieds/...-e53-lear.html
(it looks like this)

and

http://www.xoutpost.com/articles/x5/...02-bmw-x5.html
it is removed during this DIY at these steps:
http://www.xoutpost.com/images/artic...8/Img_0068.jpg
http://www.xoutpost.com/images/artic...8/Img_0070.jpg