Inside the LaCie D2 250GB (300770) external harddrive's case, is a 250GB IDE (PATA) harddrive that is 3.5 inches across in width.
A desktop computer sized harddrive. (May be a Western Digital WD25000JB)
The harddrive plugs into a small circuit board, (Bridge board), and the circuit board has a USB port on it.
Using this Western Digital Passport for an example,http://www.xbitlabs.com/misc/picture/?src=/images/storage/wd-passport-250gb/p3.jpg&1=1
Scroll down to the second photo, and left-click on it. The case of the external harddrive is shown open.
Inside is a 2.5 inch laptop sized harddrive.
An aluminum tape strip covers the small circuit board, attached at the back of the harddrive.
The second photo down on this page, shows you the small interface circuit board, that the harddrive plugs into, with the aluminum tape removed.http://www.xbitlabs.com/articles/storage/display/wd-passport-250gb_2.html
(Another design has wires coming from the small circuit board, to an interface the harddrive plugs into )
It is this small circuit board that goes bad in a LaCie. QUITE common.
1) Obtain a 3.5 inch IDE external enclosure
2) Remove the 3.5 IDE harddrive from the LaCie's case.
3) Install the harddrive out of the LaCie into the external 3.5 IDE enclosure.
An example of a 3.5 IDE (PATA) external enclosure,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1733195&CatId=2779
For additional questions please post in a Comment.