sound doesn't work properly hp pavilion g6

hello every one

i have a hp pavilion G6 working on windows 8.1 (64-bit)
this is the product number (Numéro de produit: D3F84EA#BH4)
when i try to play video games i hear no sound.
music ,films and videos on the internet work like a charm 
i just have issues with video games like( pes 2014)
i've tried almost every thing Image may be NSFW.
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any help would be apreciated guys 

i'm using uefi not bios Image may be NSFW.
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