Internet Explorer may be configured to prevent active content obtained through restricted protocols from running in an unsafe manner. This policy setting controls whether restricting content obtained through restricted protocols is prevented or allowed.This policy setting allows administrators to define applications for which they want restricting content obtained through restricted protocols to be prevented or allowed.If you enable this policy setting and enter a Value of 1 restricting content obtained through restricted protocols is allowed. If you enter a Value of 0 restricting content obtained through restricted protocols is blocked. The Value Name is the name of the executable. If a Value Name is empty or the Value is not 0 or 1 the policy setting is ignored.Do not enter the File Explorer or Internet Explorer processes in this list: use the related Internet Explorer Processes policy to enable or disable these processes. If the All Processes policy setting is enabled the processes configured in this box take precedence over that setting.If you disable or do not configure this policy setting the security feature is allowed.
Windows Components\Internet Explorer\Security Features\Network Protocol Lockdown
Machine
At least Internet Explorer 6.0 in Windows XP with Service Pack 2 or Windows Server 2003 with Service Pack 1
HKLM\Software\Policies\Microsoft\Internet Explorer\Main\FeatureControl!ListBox_Support_FEATURE_PROTOCOL_LOCKDOWN; HKLM\Software\Policies\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN
inetres.admx