Its been a while? since i set up my HTPC, its sweeet as

i upgraded to a XFX GeForce 9800GT graphics card, connecting to my TV via HDMI.
HDMI has audio and the graphics card, has a SPDIF output to SPDIF port on my motherboard, sound is from HDMI and on playback devices for sound, it shows that im using SPDIF with HDMI.

I have all my various video formats working using skark 007 windows 7 codecs,

I encountered a problem where i am trying to play a video file encoded with AC3 audio, there is no sound from my HTPC.

How do i get AC3 audio type video files working with sound via HDMI?

What do i have to install to get this working??

helpful suggestions will be appreciated

Many thanks, geekzone community

UPDATE: Forgot to tell you, i have windows 7 RTM installed 32 bit