I purchased a 13" MPB on Dec 26th 2009. I got the entry level 2.26 C2D with 2GB or Ram and 160GB HD. i have since upgraded the ram to 4gb and just updated the HD to a 500 GB Seagate Momentus. My laptop originally came with a Seagate Momentus HD. I first tried the WD Scorpio Blue 320 GB but it was very sluggish. The Seagate causes a VERY noticeable vibration and too me it is very annoying. i just double checked to make sure it was properly installed and everything seems correct. i stayed with a 5400 rpm since i have read the 7200 rpm model caused a noticeable vibration, but it seems i also have this problem with a 5400 rpm. is there anything i can do at this point...?