Different hard drives put out varying amounts of heat. If you don't think it's running particularly hot, you could use a resistor to slow the fan down a bit. If it's not a temperature-controlled fan, you might want to swap it out for one which is. Or, swap it out for a better-quality fan. Most of my kit's had the stock fan swapped out for something better: it can make a huge difference. Go for something pumping a similar volume of air at lower speed. Go for a ball/roller/pin bearing or fluid bearing if you can get the latter in the correct size.
Also, if the thing's screwed directly to the case, try loosening and retightening the screws a few times, in case they're stressing the fan housing, or put a bit of flexible material under the mounting points.
Finally, since it's new kit, this won't be a problem yet but keeping the blades clean cuts noise too. But I'm guessing you've simply got the usual cheapo fan in there.