Audio problems with a build

I've tried everything I can think of and the problem is so strange I haven't been able to find the answer anywhere else.
the audio on any videos on my computer don't work unless theyre itunes
youtube and other videos on the internet with audio have a strange scratching noise (don't really know how to describe it)
but heres the thing
all audio works fine
if i have itunes running (a song playing with itunes volume turned up) I feel like quicktime and itunes have taken over my computers audio
I would appreciate any answeres because lets face it
I can't watch videos online with Through the fire and the flames playing
thanks!