Using SDK Manager it shows Android 3.1 (API12) and that shows Google TV by Google Inc. is not installed. When I click the check box the ‘Install Packages’ stays greyed out. When I click any of the other not installed the Install Packages un-greys and shows 1 Package to install. I’ve restarted the SDK Manager and still te same.
Here is a picture of
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EDIT:
(2013-01-24)
https://developers.google.com/tv/android/docs/gtv_addon#Prerequisites
for now(2011-10-20) Google TV SDK IS WORKING ONLY ON LINUX
menu Pakages->Show Archives Details and you will see:

also see http://code.google.com/intl/pl-PL/tv/android/docs/gtv_addon.html section Prerequisites