May I add to this thread how I solved my 'no sound issues' even after having everything the way it should be and seeing the volume bar flashing as if the sound should be working!! It drove me crazy for 3 days...sometimes it worked sometimes it didn't and after scouring forums and the like to find a solution I finally found a clue. I have a Acer aspire laptop and a toshiba LCD TV and what Ive found out is.....
MOST IMPORTANTLY!! have the laptop speakers switched on for laptop only as normal WITH HDMI DISCONNECTED FROM LAPTOP BUT IN TV!!
switch TV off then back on and make sure its on the correct HDMI channel
THEN put HDMI into laptop....
THEN change the playback device to the HDMI connection to your tv
Im not very techy but with what ive read its something to do with a 'handshake' between your tv and laptop , basically if they are not introduced in the correct freakin manner they turn their noses up at each other and refuse to co-operate with each other like a pair of a** holes!
I sincerely hope my experience can help at least one person because it drove me nuts!!