You can do it in Linux with sshfs, which allows you to mount an ssh "share" as a mount anywhere you want. I use it a lot, and it works like a charm (phone still in pocket and put music on it at full wifi speed). I'm not sure if there's an implementation for windows, but maybe this will give you something to search for.
Step 1: Install the SSH server on your N900 Step 2: Read this and then try to download that (Red Drive is discontinued, but still available) Or there is also a commercial solution available (40$)