Here's a situation I don't quite understand. According to the manifest docs, I can unregister an assembly in a module upgrade by using the unregister attribute in the manifest:

<assembly action="UnRegister">
...
</assembly>

This works fine if the previous version of the module was installed. So if version 1.0 used awesome.dll but version 1.2 no longer needs it, great... works fine during upgrade. If no other module is using it, it unregisters it and deletes the file.

However, if it's a new install I get the error:

Am I missing something here? Do I just need to create a separate install file for upgrades vs. new installs? I was hoping I wouldn't, but we shall see :)

Thank you so much.