Installing Amazon Unbox Video on Windows Vista

Last night at approximately 11pm I decided I wanted to watch a movie. I don’t have cable at my apartment in Los Altos and I’ve already watched all my HD-DVDs, so watching something from a download service seemed like my best option. I have never tried Amazon Unbox Video previously, so I decided to give their 99 cent rentals a try. Instead of watching a movie last night, I wasted time troubleshooting an error message during the Amazon Unbox Video install process.
I stepped through the purchase process, downloaded the video client, and started the installation on my Windows Vista Ultimate laptop. This laptop plays back HD-DVDs so I figured it should have no problem with 800 kbps video. Partway through the install, I get the following error message:

Error: -1603 Fatal error during installation.

Consult Windows Installer Help (Msi.chm) or MSDN for more information.

I tried the install several more times with no success – even after rebooting my machine shutting down all background applications to avoid any potential conflicts. Still no luck with installing Amazon Unbox Video. The online help didn’t quickly turn up any obvious solution, so I submitted a request via email to solve the problem.
This morning, I get two possible solutions in my inbox:
1) Right-click the installer and choose Run as administrator
This solution did not work in my case.
2) Register vbscript.dll with Windows Vista
To do this, you type Windows Key + R on the keyboard and type cmd into the Run dialog before clicking OK.

Next you type the following commands:
cd c:\windows\system32
regsvr32 vbscript.dll

This results in an (apparently expected) error message like the one below:

To quote Amazon support on this error: “The output may indicate that it was unable to connect to the registration server, but you should now be able to install the program.”
This solution worked and I now have Amazon Unbox Video installed on my Windows Vista Ultimate system, but what a lousy user experience. If Amazon wrote better code, I’d never have to do either of these things. A good user experience would result in Windows Vista prompting me to elevate privileges when necessary during the install. A good user experience should register the DLLs I need to make the app work without resorting to manual intervention at the command line.
I’m probably just bitter that almost 12 hours after I attempted to rent a movie from Amazon Unbox Video, I’m still waiting to watch it, but I’d really like to see this stuff “just work”.