I've found
http://www.crazytrain.com/dd.html which gave me some idea of how to proceed. Thanks for you kind posts. Now, could the speed of the following command be improved, maybe using ibs=?:
dd if=/dev/hda3 count=1000000 skip=1000000 of=/dev/case10img2
I'm greatly interested in knowing so, any charitative soul?
Enrique.