If you can afford it
If you can afford it set up your network like this:
a windows 2003 SBS edition, which will run print server, file server, act as domain controller so you can use active directory for central authentication and roaming profiles for all users, and will allow you to secure network easily
buy a simple router just for internet gateway
if you are a bit on the cheap side then use windows 2000 server or if you are really cheap you could just use a windows xp machine as file server and print server (if you use win xp then you cannot use features like DFS, or active directory authentication, and you cannot do any of the other features which windows 2000 and 2003 have)