HDMI won't play sound

[jelly_bean561]

My computer doesn't recognize HDMI and play sound through the TV when plugged in. This was never a problem until this week.
When my computer is plugged in the TV will show the image from the computer but it will make static noises.
My boyfriends computer works fine with the same cable.
I used to have a program that would open a window whenever I would plug in something (for instance headphones) and it would ask me what I plugged in. It doesn't happen anymore and I'm scared that I may have touched some settings that I am unable to restore...
I've right clicked the audio logo and tried to set the HDMI as default but it doesn't even recognize it''s plugged in so the button is gray.
I've tried to restart my computer when it is and not plugged in to HDMI... I think I've tried every solution online.
HELP ME PLEASE!
Thanks

 

[alexoiu]

If right clicking the audio icon and selecting Playback devices, which device is checked (green)?