~~ Q: What is a computer network environment?
A computer network, or sometimes called just a network (or local area network or wide area network), is a various sized group of computers and devices that are connected via some type of communication protocol. This connection facilitates communication between all the devices and those users that are using them. You can do various things on the network like facilitating voice and video communication, sharing hardware, sharing files, data and information, as well as sharing software.
Local area network (LAN) usually refers to a closed segment of devices on a network limited by geographical area, while wide area network (WAN) usually means a much larger group of devices covering large geographical areas. You can think of the computers at work as being on a local area network and the Internet as being a wide area network.
Get more information: http://en.wikipedia.org/wiki/Computer_network
~~ Q: I have two network cards on my computer. I would like one of them to be able to access the Internet. I would like the other one to be "closed circuit". The cable for the second card goes between my computer and a router attached to some audio gear. I do not want the second card to "search" for an Internet connection. How do I disable this on the second card?
A computer set up usually is quite complicated because it requires a special configuration that is not allowed with normal operating systems like Windows XP. You need to actually run like a Server Operating System on the computer so that you can isolate the networks.
When you have a configuration with dual network cards Windows treats it pretty interestingly. Pretty much when you do something that will need the network Windows goes out and searches both network cards for the information. Which ever one provides it will be the one Windows then talks on.
You can even try things like static IPs and stopping the routes on each of the cards but ultimately Windows will still check. There might honestly be a way to do it but in everything I have researched the consumer versions of Windows just do not do this and instead bridge the network connections almost as if they were one network.
The easiest way around this is just disable one of the connections when not in use. Or think about a different way of building your network so this configuration is not a requirement to get things to work correctly. No matter how you handle it always think about security and what is safest for you and your computers.