I have a 32PF7521D TV, trying to connect a macbook to it, I have a HDMI cable that brings up the screen image but no sound, I bought a XtremeHD cable but it does not plug into the TV....?

It might work but the resolution may be an issue for your old TV.

never plug in hdmi when comp.is on you may burn your hdmi port

This is the cord i have for mine. Works fine. XtremeMac XtremeHD HDMI to DVI Cable for Apple TV
$20 online. There are cheaper and more expensive cables but i prefer to use stuff by Apple, for Apple.

Hey, you would need a Mini display to HDMI cable and unfortunately the sound cannot be ported through the mini display port.

Could be a faulty hdmi cable...

disconnect hdmi cable and shutdown pc, completely power it off. plug your hdmi cable back in to your pc and power it up. it should properly detect your tv. i use projector mode. tv must stay on while performing this procedure.

Sounds like bad Earths to me... Is it better if it is OFF, the AC/DC power supply? If so then yes, bad earthing between units and earth.

it sound like you did the right thing . The problem is the mac output for sound is bad or the TV input sound is bad.
try input a mp3 radio to the TV verify TV is working.
put an earphone to the mac to verify the mac out sound is working .
if both are working just tool around a little and you will get it. good luck

Later MacBook (Pro) use a mini-DVI connector that does not pass analog needed for composite or S-video. Was yours ever working? And most DVI connectors do not pass sound as seen by your cabling. You cannot detect display through RCA. You just set it in Sys Prefs :: Displays, try some other settings, although your seem right.
I have a white early-2009 MacBook and mini-DVI to HDMI adapter (monoprice <$10) and HDMI cable and have not connected the TOS-link for sound, yet--just slideshows at 1920x1080. You will get a much better picture digitally. -Ken

I had a similar problem with a Mac Mini.  The problem was caused by a mix-matched resolution (the Mac tries to use 75Hz refresh rate, TV expects 60Hz).  The best solution I found was to remote into the Mac (I used LogMeIn.com) and change the resolution on the Mac from a remote computer until the image appears on screen.
Process: 1) Connect Mac to a normal monitor and install the LogMeIn server (or other VNC type application) 2) Connect the Mac to the TV 3) Connect to LogMeIn from another computer (preferrably one where you can see the TV) 4) Go to Applications / System Preferences / Display 5) Change the resolution to your TVs native resolution, and change the refresh rate to 60Hz