Windows

You mean you want to establish a network, u need the PC's
a firewall, both a hardware version ( a rowter ) and a software version (MS proxy server ), You need a HUB, network adapter on every PC, and a dedicated computer to work as the server (the best computer you have )
as protecting the PC's from the users, there are many software packages that can do that , one of them is panda security, others are also available.
as for protecting from hackers, this is totally dependent on the settings of your proxy, firewall, NT settings, ETC...
Good Luck

You basically want a LAN with one fat connection to an ISP. The monitoring of user activity will be done by software. Total protection against viruses is not possible, but you can minimize the risk using above mentioned anti-virus software.
But IMHO, no offense meant, I think you should start getting into all this network stuff before you even consider starting a cyber cafe. Unless you have a partner or friend who's willing to join this venture you will end up spending up a lot of money for external IT guys, and even if thats's ok for you, you should know about the tech-side of your business, otherwise you'll get ripped off in some area, sooner or later.
good luck

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