>I have a client who wants to host a secure FTP site (FTP/SSL, aka FTPS) on a Windows XP Pro machine. I assume this would require obtaining and installing a security certificate, like for secure HTTP (HTTPS) on a Web server. Does anyone know for sure if FTP/SSL requires a security certificate to be installed on the host machine, and if so whether you can install a certificate on Windows XP Pro or does it require a Server OS?

For SSL, you do need a cert on the host. You don't have to buy one, you can create your own with SelfSSL:

http://www.somacon.com/p41.php

I have one client, uploading a file daily to a remote site. In that case we used PSFTP in the MIT-licensed (i.e. "free") PuTTY toolkit:

http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

If you want to go that route, the toolkit can generate private/public key pairs. Again, if you want to go that route I can probably dig up some client-side code I used in VFP to automate PSFTP.