Confused with Windows 8 versions? Here’s a good explanation on Dummies.com on that, describing all four flavours of the new Microsoft operating system. In short: Windows RT (limited to built-in applications), Windows 8 (for most users), Windows 8 Pro (like Win7 Ultimate with encryption, extra networking features, and similar features like to connect to a domain through a work network), and Windows 8 Enterprise (for corporate users). But here we also have mysterious Windows 8 Pro Pack, which seems to be more than just upgrade from Windows 8 to 8 Pro. It was also mentioned that you can have Windows 8 Pro Media Center Edition for those who want to record or watch live TV shows through a TV tuner with Windows Media Center and also play DVDs.
I would go for Windows 8 Pro anyway, but I just realized that Microsoft is giving away product numbers for Windows 8 Media Center Pack here. Just type your email and hit Enter. It seems that sometimes you have to wait for a couple of days for the key to arrive. But there is a hidden secret. Some people reported that it is enough to install Windows 8 Pro (x86 or x64) with public KMS client setup key (Microsoft Technet source), activate it, and then just follow the sequence: