My system which require a high speed fan and the SATA HDD is mounted reasonably close to the fan. I have noticed the fan is vibrating (not much at first but over time it gets worse) causing system BSOD and racking up "reallocated sector" numbers. Are there any vibration "tolerated" 3.5" SATA II HDD I can buy?
If you don't have any, ask at a computer parts shop for vibration-reducing mounting pads (little rubber washers) for both the drive and the fan. This will reduce transmission of vibrations through the computer frame.
Consider also replacing the fan. Don't look for high speed. Look for a replacement fan with a similar rating of cfm, and try for one that runs at a lower speed. I much prefer fans with ball bearings, not sleeve - they run smoother and last much longer.