AAM (automatic acoustic management)

Some modern drives feature AAM which lets you control whether the harddisk should be as fast as possible or as silent as possible.
You can can toggle these operating modes by using the tool 'debug' which comes with DOS - just go to DOS by starting windows in the MSDOS-mode (no DOS box!) and enter the following lines:

-oxx6 yy
-oxx1 42
-oxx2 80
-oxx7 zz

where xx must be replaced by 1f if the disk you want to setup is on the primary channel and by 17 if it is on the secondary - yy must be replaced by a0 for the disk on the channel which is configured as master and by b0 if you want to setup the slave disk.
The value of zz determines the mode you want to set - fe is the fastest and 80 the most silent mode.
To set the master disk on the primary channel to silent mode the commands would be:
-o1f6 a0
-o1f1 42
-o1f2 80
-o1f7 80

Be aware that you are talking to the harddisk controller directly - data loss could occur if you don't enter everything correctly.
For me it works really fine but I'm not responsible for any damages that occur by using this method, it may be wise to check the webpage of the disk manufacturer for tools which do the same job before trying the debug method.

Here is a small (and somewhat incomplete) list of drives that feature AAM: