9. Outlook 2000/XP Restricted Filetypes

HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security\Level1Remove

It is possible to add Filetypes back into the OK zone. This will allow you to open these attachments from Outlook (they won’t be blocked).
This key lists all of the file extensions that will be blocked by Outlook. You can edit this key to either remove extensions that you want access to or add extensions that you want to block.