Strange noise

Hi all!

I have a strange noise in my new computer. The noise is like an analog interference that comes at random times. Like the noise you can hear on the radio when driving in your car. Like static.

The noise only appears in windows mode. If I start a game the (like Call of Duty) the noise is gone.

I have my old audio board installed. So, I removed the board and used the built in audio (motherboard) but the result is the same. I have even re-installed all software including Windows 7 (new installation) but the noise is still there.

Does anyone have a clue of what this can be?

Very grateful for hints!

Best regards
Goldenkorv