According to Macfixit, the noise problem originating from the optical drive and affecting many early MacBook and MacBook Pro owners after the installation of the last 10.5.6 update of Mac OS X is linked to Growl. This software is used by other applications such as Adium, VLC, Transmit, etc. to send notification, and the workaround is to remove it till growl developers release an update to address the problem.
[translation by Linathael]
