I recently changed the stock Hitachi 250 GB 5400 rpm drive to WD 500 GB Scorpio black 7200 rpm drive. Now it was perfectly fine, no vibration or noise, just like the previous one. However now about a week past, I can feel it vibrating and that equals to the vibrations i get when I put a cd into my drive. It is kind of annoying. IS this normal? I know the drive is faster in RPM but as WD said it equals to 5400 by noise and vibrations and it was fine just a week back. (BTW Im running on a battery). There is one thing though that bothers my mind, when I changed the drive, there were those 4 mounting screws which I didnt have screwdriver for. I took it from my friend but I think I did not screw one of the mounting screws to the very end. Can that be a reason?