Quote from the article:
“When Microsoft first introduced their Media Center Edition of Windows, many saw this as a great opportunity to acquire a cheap PVR, since it was combined with a PC that could be used for the usual day-to-day tasks, such as word processing or browsing the Internet. But with that, Microsoft decided to bundle MCE with custom PCs that are built using the short list of supported hardware by big names in the industry, such as Hewlett-Packard and Gateway Computers. It could not be bought off store shelves by PC enthusiasts who already had hardware capable of PVR operations, nor did Microsoft plan on supporting hardware besides those from the few names it worked with.
Fast forward to today where Microsoft has begun selling OEM versions of their Media Center Edition to “Mom and Pop” shops to be installed on only Media Center Edition certified machines. This is a step forward, since it gives more power to those smaller shops. Media Center Edition still does not have support for the long list of hardware that MythTV does, but Microsoft has expanded their driver list quite a bit from their first release. “