We need to do the exact same thing, and we are in the same situation...if I'm not mistaken, in 4.1.6, the version we were on prior to 4.6.1, users were identified with a "x64" after their operating system when authenticated and logged in, now, they are all lumped with their 32-bit partners.
The best I can come up with is in the text box where you can communicate instructions/details for the link distribution requirement is to add a couple lines of HTML with links to the specific version of antivirus, but like you said, students may not know what they have or may not read everything. Let us know if you figure something else out.
