It took a good bit of digging, but it looks like

HKLM\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
HKLM\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List

are the two registry keys for network and workgroup profiles.

Hmm, it seems these keys are for the allowed programs that can be found in the control panel Roger mentioned. Not sure where the "blocked" program list is to be found. Maybe if e.g. Emplode was originally blocked and then subsequently added to the allow list it would work.

Edit: from the .doc file here.