Letting Users Log In From Any Machine

The question I want to ask here is mainly about an experiment I want to conduct in order to learn a bit more abou networking, network management and networking software:in my house, there are 4 machines, two laptops and two PCs.All those machines are running Windows 7 and they are on a home network in order to share the use of the internet and the use of the printers between all of them.For the time being, the users (2 or 3) just start up the machine they usually use (two are allocated to me), in other words, in the normal way things usually go on a home network.What I would like to achieve now is the following:I would like it to be possible for every one of the users to log in from any machine, and have access to their own files, settings and emails ec. from any of the machines.I know that I could (since there are only four machines and a maximum of three users) set up separate user accounts in Windows 7 on every single machine, but, for the sake of learning about the more advanced side of networking, that is the way I do not want to do this.Imagine a system manager in, let's say, a school, a school with 1,000 pupils, 250 staff and 350 machines around the building.I cannot imagine the system manager having to go around the building at the beginning of the school year, and setting up a separate user account for 1,250 people on all 350 PCs around the school, I assume he would probably do that via his server.I would probably do it the same way (if I knew how) by letting the most powerful PC (the one with the fastest processor and largest hard drive, the one to which both printers are connected too, function as a "server" (be it only a modest one, of course).I seem to remember having been told in the past there is a certain program around (by Microsoft?) to achieve this, but I do not remember the details nor the name of the software (although I would imagine there are probably a number of programs about to get to the same result).So, if any networking specialists on here could guide me further, I would love to hear about it, and I would, of course, be very grateful for any help received.