Ya it was doing that to me it wasnt that bad for me but I just unplugged my headphones and plugged them back in but if it doesnt fix it im pretty sure ur sound card is going out. :0
Just buy a new PCI sound card. They're not that expensive. Install the proper drivers & you're good to go.
Scratchy... well, first check that the connection is secure.. then check the speakers are working well by plugging it into like a CD Player instead and see how it works - if it works, its your comp (update/buy new drivers/card) if it doesn't, its your speakres..