Interoperability with existing technologies
The differences between the 32-bit and 64-bit versions of Internet Explorer can affect toolbar add-ins and Microsoft ActiveX controls. For example, 32-bit toolbar add-ins does not work in the 64-bit version of Internet Explorer. These add-ins include the MSN toolbar, the AOL toolbar, the eBay toolbar, and the Google toolbar. You can install 32-bit toolbars in the 32-bit version of Internet Explorer. However, the 32-bit toolbars will not appear in the 64-bit version of Internet Explorer.
For example, when you start the Setup program for the 32-bit Google toolbar in the 64-bit version of Internet Explorer, the Google Setup program closes the 64-bit Internet Explorer window. The Google Setup program opens a new 32-bit Internet Explorer window when setup is completed. The Google toolbar appears in the 32-bit version of Internet Explorer, and the toolbar works correctly. The 32-bit Google toolbar is not installed in the 64-bit version of Internet Explorer.
By design, the 64-bit version of Internet Explorer cannot host 32-bit ActiveX controls. Additionally, the 32-bit version of Internet Explorer cannot host 64-bit ActiveX controls.