Second David's answer below: I needed to mount a network drive automatically when users logged in. Dokan SSHFS is a nice tool, but wasn't reliable enough in this case. The copy of Netdrive I found didn't support SSHFS or sftp - not sure if a more recent one does.
The solution I'm trialling now involves adding a virtual network adapter (with file sharing disabled), using plink to open a tunnel via the new adapter to the remote machine running SAMBA, and mounting the network drive against the new adapter. There's another useful tutorial here http://www.blisstonia.com/eolson/notes/smboverssh.php.
The tunnel and network drive can be set up with a login script, so a few seconds after login users can use the mapped drive without needing to take any action.