System penetration

At a uni job fair I was advised by one of the recruiters to investigate penetration testing, most specifically aimed at Windows Server 2003. Can anyone point me in the direction of some good articles about this?
I am more interested, right now, of getting an overview of this subject.
Thanks for the help.

The first google hit for "windows 2003 penetration testing" is: http://labmice.techtarget.com/security/penetration.htm

Looks to have some useful info.

Sometimes I get so used to how helpful the forums users are that I forget to check google.
Thanks anomie