Same question here. running build 7600 (ultimate 64bit final edition) and the option isnt there at all. Sounds like great fun, so would love to try it. I have no tv tuner, but that shouldnt be necessary?
I had the same problem with my 64 bit Vista upgrade on my HTPC. I reinstalled Windows 7 using the XP instructions which is basically a clean install. Now I have Internet TV back in Windows Media Center and Netflix works(it was also missing). You will have to back up all your files and reinstall programs because everything is wiped out. I also had a problem with my blue ray DVD player and after the clean install I reinstalled software and that is now working. The only thing I had to do on the reinstall hardware wise was to update the driver on my TV tuner card. Go to Computer, Properties, Hardware Devices and make sure you have no yellow question marks for missing drivers....if so update from the internet.