The Windows 10 Technical Preview lacks many consumer-focused features including Media Center, which some have installed using their Windows 8.1 product key - but Microsoft has warned against doing so



From Neowin:

At the beginning of the month, just a day after showing off Windows 10 for the first time, Microsoft released the Technical Preview of its new OS. Like the event at which it was announced, the preview release is focused on the features that will appeal to business and enterprise customers, and is missing many of the bits that will target consumers.

One such feature that is absent from the Technical Preview is Windows Media Center, but some users have restored this feature by using the product key that they purchased for use in Windows 8.1. Unfortunately, this has created some issues for these users, which has led Microsoft to caution against doing this.

  Windows 10: If youre using the Technical Preview, dont install Media Center