How to creat a LAN with having a username & pword for each computer when they are connecting to the Network

There are probably some industrial router which would allow you do just that (this may be however relatively pricy), or you could accomplish same in bit unorthodox way if you would opt for wireless communication with cheap home router. You would need home wireless router which supports WPA encryption (and most new days routers have support for WPA – which is ONLY safe encryption by the way) and PCs equipped with wireless cards or adapters. Taking advantage of the fact that in most routers same WPA connection can be set to use many different keys (which could be used as pwords), you could set connection to use few different ones giving different key to each user (which would allow them connecting to your network). Ability of controlling when each user logged in and off would be also simply available in most router’s logs accessible from it’s interface (access to which you could secure with pword) - accessible from every and any PC of your network as well remotely from Internet. Never really thought of using router this way so don’t have any good suitable for your need example off hand, anyway because most routers doentation is accessible both online, as well manufacturer’s phone sell lines would be able to help, you could do some googline checking major names (Motorolla, Linksys, Westell, Belkin, etc) and do some reading or calling.