This is called "coil whine" and there is much to read upon the specifics, which a simple google search will yield many results, but all you need to know is that it IS normal. As for a solution, many say you need a new PSU or Graphics card, however DON'T resort to this. FIRST, try using v- sync in the game(s) in question (the ones causing the noise), and see if that works. If this does not work, you can try other solutions to this that you find on the web, but you may just have to live with it. I know it can be annoying, but you may just have an especially noisy card. Unless there is something major you changed in the system before this problem that you could revert, I think it is probably just the card. (P.S the V- sync option is usually found in the video settings of most games, and limits the FPS of the game to your monitors refresh rate. Sometimes if your GPU is outputting large amounts of frames, it "whines" in this manner). Hope I helped!!!