Some versions of Vista, such as Home, do not have secpol.msc available to change the LanMan Compatibility Level. It is necessary to reduce it for connection to certain NAS devices.
Fortunately, there is an alternate route to get thing running, other than utilizing secpol.msc. Like most things Windows, almost everything you see in the interface relates to some arcane registry key. In this case, we are going modify the LanMan Compatibility Level. We`ll just use the registry to do it!
Please note that this method requires editing the Vista registry. Editing the registry can be a bit dangerous, if values are placed in the wrong area.
First, open the Registry editor.
Next, navigate to the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
Be sure the LSA key is highlighted, and you should see some entries on the right side of the window. One of these entries is “LMCompatibilityLevel”. With Vista, this is set to 3 by default. In order to work with some NAS systems, particularly those which utilize Samba to implement Windows file sharing, this value needs to be lowered.
To change the value, double click the “LMCompatibilityLevel” entry in the right pane.
In the resulting dialog, enter a 3 for the value. Click Ok, and exit the registry editor.
After rebooting your computer, and you should be able to attach to your NAS by the method prescribed by your NAS manufacturer.