I would leave your router's firewall enabled unless you want to be hacked from the outside world. Also, DHCP should likely be enabled so keep that so.
You don't actually need to use the "Easy Search Utility" at all. Use it as a coaster or throw it in the bin
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Temporarily disable any Windows Firewall/AntiVirus/Blocker software
Use the "reset" button on the DNS-323 to restore the settings to default manufacturers settings
Open up Internet Explorer or other browser and enter:
http://dlink-xxxxxx
Where xxxxx is the last 6 characters of the MAC address printed on the base of your DNS-323. (Suggested above). This will attempt to access the DNS-323 by it's network name rather than it's IP address which is currently unknown as your router automatically assigned it one.
Login to web administration area and assign the NAS a static IP address or a friendlier name (such as "NAS") to avoid future confusion.