This update doesn't come from Windows update but from the update service built into Media center. This is the same update process the program uses get Album art. Some PCs have this service enabled by default and some don't. My Gateway did but my compaq did not so while my Gateway had internet tv immediately my compaq didn't. This is how I got Internet TV to show up.

1.Open Windows Media Center.

2. On the menu scroll up to Tasks.

3. Scroll left to Settings and click it.

4. Select General and click it to bring up a new menu.

5. Scroll down to Automatic Download Options and click it.

6. In the Automatic Download Options make sure the box next to "Retrieve CD album art, media information for DVDs and movies, and Internet Services from the Internet" is Checked.

7. Under that is a "Select download method for guide and other Windows Media Center information:"
 Make sure Download when connected is selected.

8. Under this  Click Download Now. To download updates immediatly.

9.Save and go back to the main menu. Internet TV should appear under "TV and Movies" now.