InstallAware

I have some information I need to write to the registry, but I need to do it before Apply Install. Is there a command to do this?

I think there's a "Registry Direct" plug-in on the Plug-Ins section of the forum. That'll directly execute the registry action, by-passing Windows Installer.

You'll have to manually remove the entry therefore, before or after Apply Uninstall.

Or, you can call Apply Install multiple times - whichever works for you. Each call will execute a full install routine though.