Computer Sound

Yea, uhh, when i was gaming today, i lost all sound in my headphones except for the clicking noise when you refresh of when you go to another webpage. I really need these headphones to work, and they won't. i have checked and checked the sounds system and everything says it plugged in, and I should be hearing my Marines shooting open the stomach of Zerglings. I have to sets of Headphones, one being memorex, and the other beingstandard headphones that come with a computer that say stereo Headphones. Anyway, i really need some help, and my sound system is monitered by Realtek HD. Thanks guys,

--Ambrose