I just popped in and have seen a ton of comments regarding proper imaging of a hard drive, and thought I'd throw in my two cents.
One of my favorite tools is dcfldd (
http://www.forensicswiki.org/wiki/Dcfldd and http://www.sourceforge.net/projects/dcfldd/). It is a forensic version of dd, that can be used over a network. It essentially does the same things that many have been describing, but in a much cleaner interface.
A snippet from the wiki:
-------- snip -------
dcfldd is an enhanced version of dd. It has some useful features for forensic investigators:
The program only produces raw image files.