Using Linux to quieten your computer
Optical drives
Modern CD- and DVD-rom drives spin very rapidly causing much noise. Compromising speed to lower the noise can be done by lowering the drive's speed. There are a few ways of doing this:
hdparm -E [speed] [cdrom device]
echo current_speed:4 > /proc/ide/[cdrom device]/settings
setcd -x [speed] [cdrom device]
Another way is increasing the readahead. Note that adjusting this is tricky since it might result in the drive spinning down after a read just to spin up again. This acceleration could cause a lot more noise then the drive simply continuously reading the disk.
hdparm -a[sector readahead] [cdrom device]
echo file_readahead:[bytes to read] > /proc/ide/[cdrom device]/settings
Duron/Athlon (XP) processors
Due to some odd and mysterious reason AMD Socket A CPUs don't save power when they are idle (at least not as much as possible) unless you explicitly tell them too.
These processors can run A LOT cooler if you ask them too. The intricate instructions and explanations are found in the Athlon Powersaving HOWTO, or you could just use athcool