Hi,

"Does COM interface allow you to cross 32/64-bit boundary?"

Quote from http://www.windowshpc.net/Resources/Documents/64-bit%20Insider%20Volume%201%20Issue%207.pdf
"Any COM component that is currently being used out-of-process should not present a problem when you are migrating to 64-bit Windows, because Remote Procedure Calls (RPCs) can cross 32-bit and 64-bit boundaries without any problems.”

inprocess components (dll): no
out of process component (exe) like Excel: yes

Regards
Christian