We need to transfer thousands of small htm files up to a web server running IIS7.5 on Windows Server 2008R2. The files are grouped in folders, each folder containing from 200 to 500 files. Remote Desktop Connection's drag-drop isn't working very well for this. Often it gets stuck at "calculating" and never seems to progress. So we would like to enable SSH file transfer on the server.
There is no native feature to "enable SSH file transfer." IIS includes an FTP server, which has an FTPS feature, but nothing for SFTP (which, as you're aware, is a sub-protocol of SSH.)
You'll have to find a 3rd-party SSH server that supports SFTP; there are free ones and commercial ones for Windows. This site isn't a good one to ask for product recommendations, please read the FAQ.
You could also enable WebDAV over HTTPS, and then you don't even need anything on the client more specialized than a browser, or even a mapped drive from a Windows machine to the WebDAV server.
Any protocol is going hurt because you are initiating thousands of connections over a network link, and each one will have network-delays as it starts up. Also WebDAV is a nice idea, but has proved a very temperamental thing for me before - this post and comment illustrate some example annoyances.
The simple workaround is compress the files up, copy the zip over RDP in one operation, then extract it on the server.
Regarding SSH servers, I've used http://www.freesshd.com/ before, but I don't know it well enough to leave it running long-term, and https://filezilla-project.org/ as the client. They will also do for a one-off sort of copy.