We are a group of mixed computer knowledge looking to setup a shared linux/win32 environment where people can come in, pay for there time and then either spend it web browsing/working on the linux machines or spending there time gaming on winXP machines.

The setup we have so far is:
One linux server, fedora 5 acting as a PDC with roaming profiles.
4 WinXP gaming machines.
4 Linux fedora clients.

All connected together via a switch, internet access is provided by a router & modem.

The part that has me scratching my head is how to have it so people pay for time anonymously or have an account and then have it so the server can lock the clients automatically if there time runs out. Also, time has to carry over sessions.

I had a quick look for existing software but there appears to be little that runs on a linux server, only win32.

Any suggestions as to how we could achieve this?