A comment by poster "Zaphod Beeblebrox III" helped me find it:

Microsoft Showcase: Windows Media Center: Netflix and The White Gloves:

...you have to go to Tasks -> Settings -> General -> Automatic Download Options in Media Center and then click the button to run the update manually. Then, a new option for Netflix shows up under the Movies section and the prompts guide you through an easy Netflix installation.

However this wasn't obvious, I even went into the "Automatic Download Options" page, but it appeared to just be for album art and such, it wasn't until this comment sent me back that I saw the manual update button, which then prompted me to "setup Internet", which seems odd since I can't figure out what the setting up process did...