I built this PC about 2 months ago, and it was running nice and quiet, but I turned it off for about 4 days and when I can back and turned it on, it's suddenly loud. I see no dust buildup and it's running cool, so I'm not sure what it could be. I don't think they're running at 100% but they are running significantly more than they were before. Even changing fan settings in BIOS hasn't fixed the problem.