title says all basically. i have a new set of speakers for my computer, plugged into the audio jack. the speakers work when i'm playing music on my iTunes perfectly, but when i try to play videos on youtube, the audio doesn't come out [it did before, but my bro did something]. anyone know why?

is the slider on screen over to right?

Are you able to adjust the volume slider on YouTube? Have you checked the "sound and audio devices" area in Control Panel?