I purchased an Antec SmartCool 120mm fan(http://www.antec.com/Believe_it/product.php?id=Nzk=) and a Scythe “Kama Stay” multi purpose solution(http://www.scythe-usa.com/product/acc/071/sckst1000_detail.html). I placed the fan on the Kama Stay and stuck it in a PCI slot. When I turned on the computer, I can hear vibrations. At first I thought it was my computer that was vibrating, but then I realized that it was actually the fan. Therefore, I tested it by connecting it to my Scythe “Kaze Master Ace” fan controller(http://www.scythe-usa.com/product/acc/045/km02_detail.html). Reducing the speed of the fan from 1200RPM’s to 900RPM’s, silenced the vibrations. Therefore, it was verified to be the SmartCool 120mm fan.
I currently am using a Coolermaster silent fan(http://www.coolermaster-usa.com/product.php?category_id=1655&product_id=2889) instead. It does not vibrate at maximum speed. My computer is fairly quiet. I have 2 front intake fans, 1 rear exhaust fan, and 1 fan cooling the graphics card all running at 720RPMs. The CPU fan is spinning at 367RPMs at idle. The first 4 are controlled by me while the CPU fan is controlled by the motherboard.
I will have to try again with another computer to see if the problem is really the Antec Smartcool and not the computer.
A possible solution I will have to try is to use rubber washers available at any hardware store. I do have some available, but that will have to be done another time.
As of November 12, 2009, I have successfully added the Antec smartcool to my system. Since it is touching the side and the bottom, I stuck floor pads on it to silence the fan. These are available in most hardware stores. Using zap straps, I converted it into a top front intake fan.
Some customers who tried the Antec smartcool 120mm fan at http://www.memoryexpress.com/Products.aspx?ProductID=MX1689%28ME%29&curtab=2