File sharing over LAN

Okay, I have several questions/problems. First of all, I just bought a 1 TB external hard drive to have all my video on. Now I want to share this with my Xbox and laptop, and I have no idea how. I have had problems with the UPNP service not starting which I fixed, but I still don't grasp the concept of sharing over LAN. I have made the external hard drive public on the network but I don't know how to access it on my laptop. Also, do I have to make the laptop able to connect to my computer or does it do that automatically?

Continuing, I am wondering if I can connect my external HD to the router if I have a USB port on it, thus not forcing me to have a computer constantly on for sharing.

Do I have to use Windows Media Center to connect my Xbox to the computer? Also, I can't see the Xbox on the Windows Media Center devices list and I can't either see my computer on the Xbox devices list, but I can see the laptop (which I haven't done anything with), although I can't access it.

Finally, if I have to use Windows Media Center to share video to my Xbox do I have to run it every time I want to share video with my Xbox?

I'd love some help to understand the whole network sharing, but none of the websites I found explained it in an easy way. Also, this is written in a hurry so bear with me if my phrasing isn't the best.