I can hear my drive being accessed all the time. Its not unusual for laptops as they vibrate more than drives installed in the chassis of desktop machines. As you've no doubt noticed, the slim drives in laptops are mostly plastic..
I noticed also when I installed a 7200 Rpm black scorpio hard drive that I can hear it accessing all the time now too.
Is it lightscribe? My dvd burner in my lappy is, and every lightscribe drive Ive ever owned in any machine is quite a bit louder than standard drives.