How to silence DVD ROM
The default setting for the DVD ROM on the T4x models is very noisy.
It isn't obvious, but there's a BIOS setting under the "Power" section in which the drive can be set to silent. It is very effective.
Another solution is to use the command hdparm :
$ hdparm -E8 /dev/hdc
-E8 sets the speed of the cdrom drive to 8, which is silent, to reset maximum speed use -E0.