I received some emails regarding my previous post on code signing, so I have added two new videos to my website from the Basic MSI course for InstallShield 2009. You can view them on the following page:
Or, you can just go to each individual movie's page. Here is a movie on the steps that are involved in digitally signing files:
Here is a movie on how to sign files from within the InstallShield 2009 IDE:
I hope this helps to clarify your thinking on this. Enjoy.