Alright i aint that good with computers but i know most things. Im trying to fix my lil nephews computer. It had sound before he went and did some shit to it. It has no sound or volume control. I get a error msg saying something about..."There are no active mixer devices available... then tells me to go add hardware."

Is this problem caused by a driver or something else i looked all over the web and tried everything. Any help would be greatly appreciated. REPS will be given the first person who gives me a solution to the problem!