Recently I bought a new GPU: GeForce GTX 550 Ti, and after installing it I get a strange buzzing sound. It's not always there, just sometimes (mostly when I open some game, but sometimes also in browsers etc.).

It's not a capacitor or a fan, as unplugging speakers from sound-card makes the 'bzzzzzzz' go away. However, muting windows doesn't mute this sound.

I'm pretty sure it is fault of the new GPU, but how is this happening and can I fix it?

Can it be a low power supply? I thought of buying a stronger unit, but as everything works, and computer doesn't shut down, I hesitate.