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In this case, since you are referring to HDMI audio, it is integrated to the graphics driver.
The last available graphics driver for your processor (from our website) is for Windows 8.1* 32 bit, which means that it is an incompatible driver for your laptop.
I would recommend downloading the latest graphics driver available (for Windows 7*) from Asus' website and install it using compatibility mode.
If you keep on having issues after this, I would recommend contacting Asus Support.
Hope this information helps.
Please don't hesitate in replying this post if you need further assistance.