What do I require to run multiple web sites, each with their own unique domain name, on a Windows 2003 VPS ?
Yes, it is possible to host unlimited websites on a Windows VPS. You can host all the websites on a single IP as well. You just need to make sure the websites have 'A' record pointing to your VPS IP. The 'A' record is set where the DNS of the websites are hosted. BTW, if you are not sure how to host them manually, go for the Plesk control panel.
Thanks for the info. I will look into it further as it sounds promising. I understand that the A Record would direct users to the IP address of the VPS, but am not sure what happens when the request hits the server.
When the request reaches the server using an 'A' record, it check the VirtualHost entry (in Linux it's called VirtualHost, not sure what it's called in Windows) of the domain. The VirtualHost contains the DocumentRoot of the domain (DocumentRoot specifies the path to the website folder). Each domain has it's own VirtualHost entry. The request then goto the DocumentRoot of the domain and search for the file that needs to be served first. The file which need to be served first depends on what "DirectoryIndex" is set. By default "DirectoryIndex" is set to, index.html, index.htm, default.html. You can change it as per your wish.