A computer that has Windows Internet Explorer 7 installed is running Windows Vista, Microsoft Windows XP, or Microsoft Windows Server 2003 in an Active Directory domain environment. However, the Add button in the Trusted sites dialog box is unavailable. You cannot add a Web site to the “Trusted sites” zone even when the current user account belongs to the Administrators group.

This problem occurs if the “Security Zones: Use only machine settings” Group Policy setting is enabled.

Note: When Microsoft Internet Explorer 6 in installed, members of the Administrators group can configure the “Trusted sites” zone regardless of whether the “Security Zones: Use only machine settings” Group Policy setting is enabled.