No sound on my computer

hi im new to this but here goes. I was trying to listen to music on my pc and it tells me i have no sound devices or something. One of my friends say it sounds like i erased a sound device. But that did not help me any. how can i get my sound back?
 
Take a look in the Device Manager (Start > Run > devmgmt.msc > Ok) and see if there are any devices with yellow question marks next to them.

What is the brand and model of your PC or motherboard?
 
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