I guess you mean you can access the NAS trough the windows' file sharing.
I shared a folder "upload" on my own computer "2510p", so the path is \\2510p\upload.
Then i entered the network explorer, in 2510p, and drag&dropped the "upload" folder on HFS, as virtual folder. It works, and it can be expanded to see what's inside.
Then i made another try: i mapped that folder to drive N: and, from "my computer", i drag&dropped on HFS. The story was the same: it works.
Is there anything i'm missing?