Thanks to you all for your help. I'll take a look at nLite, Patio.
So, to summarise, one way is to do this (if I have understood correctly):
The Server
1) The server needs to install RIS (Remote Installation Services) through the Control Panel. The Windows installation files of a clean image/disk are installed onto the server hard drive. Once the files are copied to the server's hard drive, right-click the directory containing the installation files and choose 'Sharing'. This configures permissions for client access.
The Client
2) In each computer's BIOS, the client machine needs to boot using the network card. This forces the computer to query the network for boot files. The client computer finds the RIS server and RIS instructs the client to install Windows. Since Windows installation files include boot files, the client machine is able to boot and start the installation.
Is that correct?
Thanks again.