Website virtual directory

Win 2000 Prof. – I want users to be sent to my server from a link on my website. When they hit the server they are given the username and password login window. After entering their user and password they are sent to their virtual directory where their website opens in their browser. I don’t want them to be able to navigate or have access to any other users directory. I have setup the server and the virtual directory which works great with ftp, but if I setup a web virtual directory the user isnot sent to his directory unless I include the directory in the link(ftp.server/user1) which I don’t want to do. Is this possible? Any ideas? Why would it work for ftp but not web? Thanks