This relates to "home" version of Windows using a workgroup with only one user account on the system.

After the most recent update, I am unable to change the update settings. The "Important Updates" dropdown is greyed out and I am therefore unable to make any selections.

Any suggestions? (Keep in mind that MMC, gpedit, or secpol do not exist on this platform.)

You may have to use the registry to change the settings.

This link has a list of registry entries for windows update and many other settings.

http://www.microsoft.com/en-us/download/details.aspx?displaylang=en&id=25250

Windows 8.1 Update and Windows Server 2012 R2 Update 1 .xlsx

This excel file has a huge list of registry entries. Near the bottom there is a "WIndows Update" section that should have the relevant keys and settings.

OK, found that and a likely candidate: Configure Automatic Updates.

Which, if any/all of the five registry entries, should be modified (and to what values)?

HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate\AU!NoAutoUpdate;
HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate\AU!AUOptions
HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate\AU!AutomaticMaintenanceEnabled
HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate\AU!ScheduledInstallDay
HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate\AU!ScheduledInstallTime

• Edited by PuzzledAfterUpdate 13 hours 16 minutes ago

Hi,

Here is an article about those registries, please go through it:

Configure Automatic Updates using Registry Editor

https://technet.microsoft.com/en-us/library/dd939844%28v=ws.10%29.aspx

Regards,

Yan Li