This explains in Visual Studio terms what happens, but it's also how
InstallShield works.

http://www.simple-talk.com/dotnet/visual-studio/build-and-deploy-a-.net-com-assembly/

Briefly, InstallShield has a Register for COM interop option at the
component level that runs regasm to create a .reg file that gets added to
the MSI file at build time (one of the options tells InstallShield where
regasm is, and it runs it with the /reg option). So the "right" registry
entries get added to the system at install time from the MSI file. That
InstallShield Register for .NET COM Interop option might be all you need to
do.