Viiv under the Hood - Software
The heart and soul of a Viiv machine is Microsoft Windows XP Media Center Edition 2005. Or, in the coming months, Windows Vista Ultimate Edition, which features the Media Center application as part of the install.
Interestingly, the Viiv prerequisites don't include a TV tuner, which is a bit odd. But perhaps it's because Intel doesn't really care what sort of tuner card you use. Windows XP MCE does require a tuner card, and they do care what sort you use, so just stick to their guidelines.
All the software Intel has released so far for Viiv machines (drivers, etc) is geared to run on Windows XP MCE, so there's no question about using an alternate configuration like MediaPortal on Windows XP. It's not that such a setup wouldn't work, but it would break the requirements for Viiv and the Intel updates wouldn't work. It would also run into problems trying to use DRM-protected content.
And Linux/OSX systems have been left out in the cold. Some people are naturally frustrated with Intel's close partnership with Microsoft, feeling that it's yet another example of stifling the competition. Whatever the reason however, there's no doubt that the Viiv experience will in reality be a Microsoft experience.