what version of Windows? 7? 8? is it 64bit? (Windows 8 is better concerning Extender support)
what version of my software is installed?
Did you modify the installation during install?
links to current releases are on the Setup and usage
choose to use the [x] SUGGESTED settings and answer YES to the LiveTV question.
THINGS NOT TO DO:
Did you install AC3Filter?
Did you install anything from Divx?
all audio formats such as TrueHD, DTS/MA Vorbis are converted to AC3 for Extender playback
Many video formats are supported. Such as FLV, EVO, MKV, OGM etc.
close Media Center on the Extender before making changes
press [Reset All] - test with no other changes - need more help?
go to the MKV TAB and try selecting the 'Alternate' setting for Extenders.
Read here About filetypes
such as mkv on the Xbox 360