Hey i bought a Radeon HD 5770 and an HDMI MNTR ACER|LED 21.5" 5MS S211HLBID R to go with it. After installation of the devices into my computer and installing the Radeon Drivers there was no more sound. I am using the AMD HDMI device set up as my default sound device as was told to have set up. Only thing i can think of though is to try to change the bios when restarting my computer for the sound as i have seen on many forums. But i would rather use another method before trying this out quite yet. Which makes me think that my sound card maybe doesn't support HDMI sound or something and if there was sound cards that could support HDMI it would be appreciative if you could mention something of the sort.
I have found out the reason behind it and it's all fixed. Didn't realize it automatically switched sound devices when i plugged in my HDMI cable to AMD HDMI which there was no sound for. Switched it back to speakers as it's default after i plugged in the HDMI cable and it seems to have been fixed.