Cannot disable password expiry on Server 2012

I have an internal only Windows Server 2012 which I want to disable the password policy on. (The server is also a domain controller, if that makes any difference.)

I've tried following the instructions on this helpful blog, but when I double click on any of the entries, the control on the properties dialog (to set the value) is disabled.

I'm logged into the server as an administrator, and I've open the Local Security Policy as an administrator.

Can anybody explain why I'm unable to change these values?

(Please be gentle, I'm a programmer, not a network guru.)

You're trying to edit this setting using the Local Security Policy editor but the setting is configured in Group Policy and that's where you need to change it.

@Joe sent me in the correct direction, and from his comment I found this blog via Google.

The bit in particular which was useful was a comment left on the blog...

On my server, these settings are disabled under the Local Security Policy (WS2012 Essentials.) However, they can be changed under the Group Policies.

From the charms, search Apps for “gpmc.msc” and start it. Group Policy Management -> Forest: YourServerName.local -> Domains -> YourServerName.local Select “Default Domain Policy” then right-click and select “Edit…” to open the Group Policy Management Editor.

Group Policy Management Editor Computer Configuration -> Windows Settings -> Security Settings -> Account Policies -> Password Policy