I notice something last night. My dell notebook went toast on me, so I got a USB 2.0 2.5" external case for the drive so I can use it for my desktop. When the drive was in my notebook, it made a lot of noise. Now, it is silent and I didn't even put the cover on or screw it in yet. Does anyone have any idea on why? Is it because USB 2 is slower than the IDE so it is writing/reading slower?
I'm pretty sure the RPM and other stuff is constant no matter what interface you use. 4200 RPM is normal for laptop HDs. Probably the laptop case strengthend the vibration noise a lot.