no sound

I have an inspiron 1525. have had it connected before to my home theatre system via an hdmi cable routed thru Sony 7.1 reciever. Up until recently everything worked great, great picture great sound. Hooked it up last night to stream a movie, which i have done before with old episodes of '24'. Now there is a picture but no sound. Checked the cable tried, another one, both work fine when connected to the bluray and dvd recorder, but when either cable is used to connect the computer to the home theatre system there is NO sound, just a picture. My sony receiver recognizes the hdmi connection but as soon as I plug it into the computer, the speaker icons on the sony's display go out. Unplug it, and they wink back on. I am perplexed, checked the audio setup and the hdmi is the default connection. the built in speakers work, the outboard speakers work when plugged in, just no sound thru the hdmi when IT'S plugged into the system, when up until a few weeks ago (the last time i watched something online) everything worked great. Any ideas.

 

I was under the impression that HDMI on a Dell did not output sound, but found this:

No sound through HDMI connection to TV - Laptop General Hardware Forum - Laptop - Dell Community
http://forum.notebookreview.com/dell/232369-hdmi-laptop-amp-no-sound-but-picture-plasma.html

Apparently, you need to change the default audio from the onboard to HDMI.

 

Found the problem. I have windows 7, and it comes complete with 7.1 audio output from the hdmi output, thanks to sony. Authorized it, disabled the speaker connection, and away she went. So yes the hdmi on a 1525 definitely
does output video AND audio. Yeah for me.