From what I have seen in my setup, Vista actually detects the DNS-323 as a PC and a storage device (two icons). The one that asks you to install drivers is the storage part. As stupid as it sounds you don't need to use this one for anything (so far). You can connect, store/share files, etc. via the PC device.
Now, if you don't see the two DNS-323 PC icon on your network it may mean that your Vista PC/laptop is not configured to use Netbios. This happened to me with a laptop in my network. Once you enable Netbios you should be able to see the 323 as both a PC and storage. Again, just connect and map the drive via that icon.
I know this doesn't directly answer you question, but it was what I found out after trying to find drivers around the web...