According to a report released by ABI Research, the number of PCs running home theaters could grow to 25 million worldwide by 2013.  Microsoft Vista and the Windows Media Center application are helping drive growth in the HTPC market. With the introduction of the Windows Media Center in mainstream PCs, Microsoft is allowing more and more consumers to appreciate the value the platform brings to living room entertainment.  

You can learn more about the study at http://www.abiresearch.com/abiprdisplay.jsp?pressid=1086.