As you might know there is no good way to control the installation or blocking of ActiveX controls for standard user accounts. Windows Vista introduces a cure to this, and it is called ActiveX Installer Service. This service is not installed by default but can be found in Programs and Features > Turn Windows features on or off. I recommend that you add this component using an unattended answer file in corporate environments. Once installed you can control if a standard user should be able to install certain ActiveX controls or not. I have not found any good step-by-step guides for configuring this so here it comes:
1. When you go to a web site and try to install an ActiveX control, an event is logged in the event viewer specifying the exact origin and http or https address where the ActiveX control resides.
2. Enter the address you found above in the group policy setting “Approved Installation Sites for ActiveX Controls” found in Computer configuration\Administrative templates\Windows Components\ActiveX Installer Service with the additional settings for example 2,2,0,0.
To allow for instance the Windows Genuine Advantage to be allowed to be installed by a regular user you can add the address http://download.microsoft.com with 2,2,0,0. Now you can refresh the policy on your test computer and go to Microsoft Download Center and there try to validate and install the WGA ActiveX control as a regular user account without administrative privileges. Voilà!