Originally Posted by Boreas
I would have suggested that you move your sound card to another PCI slot, prefferably waaaaay at the bottom to eliminate potential noise source but since you took care of it nm.
Another reason why it may have happened is because the volume for the microphone is not set on mute.
If it was staticy when you moved the mouse this was probably an interrupt issue (or some other shared resource)
By moving the card to a different slot, you change the resources that the card will use and this can sometimes solve conflicts.