Please help! HDMI audio not working

Hi, first of all, I am new here so I really apologise if I have put this in the wrong place but I need help urgently. I have looked at another post similar to my problem but it didnt help me. I have recently installed windows 7 home premium 64bit on my sony vaio vgn-fz38m laptop. I had problems initially getting the graphics card to work but have managed that, my main use for my laptop is watching my edited/downloaded files on my plasma screen which with vista I had no problem connecting to via HDMI. Now since installing win7 I have had nothing but problems, I have tried disabling/enabling drivers and hardware and uninstall and reboot for windows updates to find the right driver and have just downloaded nvidia driver for HD but it says it cant find the driver so didnt install. I have picture fine through the HDMI but no audio,

Please can someone help me......

I am using nvidia geforce 8400m gt graphics and the sigmatel HD audio codec but the sound settings show my digital output (HDMI) as not plugged in.

I have googled and tried every known idea and I am hoping someone can help my specific problem.

OK so I did a system restore to a point when I got the sound working for a very short period. On start up I now have the HDMI codec as enabled and I have set it to default service, however the sound is still only coming from the laptop! I have tried test on the HDMI speakers and it says failed to play set tone.

Can someone please help me once and for all, as this is my third day of trying to configure my computer since the installation of windows 7, and I am getting really frustrated, especially as it was working briefly until I had to do an update then it disappeared again, hence first post....

Please help

Sorry taken so long to get back to you and thank you for your reply, I had to have a break but still no luck, here is what you asked for...

Speaker/Headphones which is ready and default device

and Digital Audio HDMI which is now 'not plugged in' again, the only way I could get this to work was by uninstalling the codec/controller but then still no sound being sent, so either way something not right. The trouble is whenever I do the uninstall and reboot my system doesnt like it and crashes after a period.

My specs are up, but it is a IDT high definition audio codec

Thanks, I have now figured out it was the graphics card not the sound card so I have rebooted in safe mode and uninstalled my nvidia geforce 8400m card then rebooted which reinstalled the original driver, so hope that side is sorted.

However, this was my original problem as I would like to obviously use my hd plasma and plug it into my laptop, so can I ask what driver you suggest to upgrade to that has compatibility and and for a dual monitor?

Thanks again for your help and I realise now this is in the wrong thread as its for sound and audio when actually its my graphics card but I wasn't aware at the time...

Ok thanks, I will try and let you know