I don't know if you're willing to do any coding yourself or not but there is a fairly easy (I think) way of setting up an internet cafe.

• Set up one computer to act as a gateway to the net.
• When a customer buys time on a PC, add that PC's IP to the firewall's "allowed" list.
• When customer's time is about to end, send a windows message to that machine so that they can either save their work or buy more time
• When time's up. Remove/disable that PC's IP in the firewall.

Things that you'd have to do on your own

• Find firewall/proxy software that would allow you to update its configuration programmatically and/or via a command line utility
• Setup the firewall/proxy
• Write a small Perl daemon for keeping track of usage times (this is probably the easiest part)

You may find that using a UNIX-based system for the gateway may be a lot cheaper and more reliable/flexible than using a Windows box.

My 2c.

--perlplexer