sounds like a hardware issue... power supply interference, etc.. I've also seen cases where just switching the CPU stopped the interference (while keeping the same exact hardware: MB, Power supply,memory - everything). I have also found that if the Intel SpeedStep feature can cause interference on some on-board sound cards -- you can try disabling that feature if available. Still, most likely a hardware issue that probably gets worse when you use more of the CPU (i.e. inside RR). You can download/install another player (i.e. Foobar2000) or an old version of RR (and/or other frontend) and verify that the problem will persist -- which will rule out a software issue.