Windows SCP using key files

Hello all,

I've come across a situation where I need to download files via SSH
from a *nix machine to a Windows server. We are running the Windows
server and will be accessing the customers' nix server, hopefully
using a public/private key. We will have the private key here on our
Win machine and will transfer the public key to them. I am able to
generate to the pub/priv key using puttygen, but I am unsure as to the
next steps. I'm aware of cygwin, but that seems overkill for one
command. I also don't know how I would set that up. This will be an
automated procedure, as we have to grab files every night, perhaps
more frequently.

I've done pub/priv key auth between two Linux machines, and have even
automated it. I'd like to grab the files via a Linux machine, but the
files will have some post-download functions performed, and that part
can only run on Windows.

Any suggestions or comments you can provide would be helpful. I'm sure
someone has encountered and successfully solved this before, but 'the
google' hasn't helped much.

Thanks in advance.