Yaobing,
Because the MC12 forum is temporarely closed, I put my post in this forum.
You know about the problems I have with configuring TV in MC12 (I wrote about it in the MC12 forum and emailed you).
Well, I have figured out the solution. I copied the [HKEY_CURRENT_USER\Software\JRiver\Media Center 11\TV Settings\PreviewMediaType] key and the [HKEY_CURRENT_USER\Software\JRiver\Media Center 11\TV Settings\TV Channels] key from the registry to the Media Center 12 part of the registry.
And now I can watch TV in MC12 as I already could in MC11.
The only thing that doesn't work yet is that when I click Options in TV Tuner I don't get the Options window with tabs but 'Starting TV' and 'Failed to play TV'.