I've done all kinds of google searching on this topic, and everyone
seems to say the same thing:

In a Visual Studio Setup package, if I want to fail an installation
based on something found in my custom action code, then I just throw
an InstallException and the runtime will be informed that it must
rollback. The only problem here is that the error message displayed to
the user contains information they don't need to see like the method
name being called, etc.

If I'm going to rollback, I want to be able to display a message box
of my liking to the user in a way they'll understand.  For example,
let's say that I'm installing an application that has a dependency on
Internet Explorer 6 or higher.

I could throw an install exception like this:

throw new InstallException("This application requires you to have
Internet Explorer 6 or higher installed.");

But the display that comes up shows some nastiness in it regarding the
method that threw it and so on.  What I want to do is this:

catch (InstallException instEx)
{
MessageBox.Show(instEx.Message, "Installation Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
Rollback(savedState);
}

However, what winds up happening is that the Rollback method winds up
throwing its own exception about how the savedState dictionary does
not contain the expected values.  So now what am I supposed to do
exactly?  Do I need to change the savedState dictionary in some way?

Thanks for any help anyone can give on this.
Stephajn