Make sure you have downloaded and installed Rollup2 for windows media center 2005.

It gives you new features:

  • Connect your xbox 360 as your windows media center extender
  • Support for up to four tv tuner cards
  • Away mode
  • Convert HD TV shows to standard definition and burn to a DVD
  • Burn to a DVD from other network locations, like a PC.

Make sure you have enabled Automatic updates in windows media center 2005.