Static(?) on the radio.

Every once in a while I will receive what sounds like static from ATC whenever they communicate with me or another airplane. It doesn't happen all the time, and I can solve the problem by pressing the Q (sound on/off) button. Once to turn off, then again to turn on. I have an antiquated Dell 2400, on board sound, 1 gig Ram :-[. Is this just a little bug, is my computer to blame? I plan on a major computer upgrade soon, but am curious as to what is causing this small, but anoying problem. Great many thanks in advance.