Don't know the site so I won't check it, but what do you mean by mosquito noise? What peak frequency? What harmonics? Try running that thing through audacity or another software with Fourier/wavelet transforms (temporal sliced transforms are better) and posting an image instead.
Usually the culprit for clear tones in audio is power related, either at the mobo or PSU, but hard to know. You can try using a powered USB hub (separate wall adapter type) to isolate the power as much as possible. Also, if you have anything that has a ton of LEDs or case lighting, remove them and test again.