For setting up a cyber cafe with 30 computers in lan you should proceed as follows-
Hardware: configure one of your computer as windows 2000/2003 server for which get a machine with the following configuration--
Atleast a 3 GHz processor with good quality motherboard.
atleast 1GB DDR2 RAM(the more the better).
A good quality PCI-e graphics card (atleast NVEDIA 6X series)
A good smps with atleast 450watt power supply.
80 GB hdd.
a sony DVD writer.
A 19" monitor.
Two ethernet cards(If your motherboard has one built-in, then one card).(As it will be the gateway for your internet connection).
Two Dilink 24 port switches.
Since it is a cyber cafe, so, many people will come for gaming.So your client machines should have atleast 512MB Ram and GForce 6200fx(atleast)card to support all latest gamings.A celeron D processor is sufficient for this purpose.
Since the prices of 17" monitors have come down, Use it in the client machines
Install winXp professional on the client machines.
Give a good power backup to all the systems.A 1000VA UPS for every two machines will be ideal.The server should have separate UPS without any sharing.
Install Kaspersky antivirus on all the machines.It gives the best protection
on the lan environment and internet.use a good spyware remover like spybot
in all the machines.
Make ghost cds of your client machines(since all of them will have same config, so one set will do).The server machine should also have it's own ghost.
Each client machine should have the following software installed--
DirectX 9c
Winzip
winRaR
dotnet runtime
divX codec
Acrobat reader
Media player 9
Klite mega codec
shock wave player 10
MS Office 2003
(Except office, all are available in digit cd)
Server machine must have all the above softwares also plus the softwares I mentioned earlier.
If you require further assistance on how to configure them, reply in this thread.Go for Dataone Unlimited as your internet connection.