Comment 64 for bug 568120

@ cmcginty:
For testing purposes you can use this command in the terminal (use copy/paste):
sudo hdparm -B 254 /dev/sda

Press Enter. Type your password when required; this will remain entirely invisible, not even dots will show, this is normal.
Then press Enter again.

As Jan Claeys already described, you can make the hdparm change permanent as follows:

In the terminal (use copy/paste in order to avoid typing errors):
gksudo gedit /etc/hdparm.conf

Press Enter.

Now Gedit starts with a text document. Add the following lines at the very end of this text document (use copy/paste):

/dev/sda {
    apm = 254
    apm_battery = 254
}

Save and close the text document. Now reboot your computer. You're done. :-)