you may need to enable LLTD support or it wont work in win7
i had to enable it to get it to work

LLTD (Link Layer Topology Discovery) is not required to map or use a DNS-323 in Windows 7 - all LLTD will do for you is allow Windows 7 network map to draw a pretty picture, but you can map a drive and read/write data without it.
Same goes for the Windows 7 drivers for the DNS-323 - it'll give you a nice picture in devices & printers - but they're not required to actually use the NAS.