Hey, first of all let me say that I am no expert at all.
But one thing that can make things easyer to learn more about network security and about the different kinds of operating systems are to run your own network with multiple operating systems on it. Now that can get alittle expensive because computers arent really cheep, and u have to buy equipment like hubs and ethernet wires etc.

Well most of you newbies dont have all that, i suggest you learn more about networking with a program called VMWare ( http://www.vmware.com )
You can run multiple computers on one machine(with enough resources)

Lets say you are trying to find a way into a certain linux operating system, well if you run windows you can actualy put a virtual machine of this version of linux on that windows box and run it, learn more about it and hack into it from your windows box if thats what you prefer.

This is just a nice legal way to learn more about network security and hacking.

Id like to hear some feedback so e-mail me or post a replay!