How to disable automatic machine account password changes

Start Registry Editor. To do so, click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
In the right pane, click the
DisablePasswordChange entry.
On the Edit menu, click Modify.
In the Value data box, type a value of 1, and then click OK.
Quit Registry Editor.