preferences backup

where is the preference file stored.
I want to make a copy if I need to it.

OSX: /Users/{user}/Library/Application Support/Blender/2.5x/
or
/Library/Application Support/Blender/2.5x/

Windows: C:\Users\USERNAME\Application Data\Blender Foundation\Blender\2.5x
or
C:\Documents and Settings\All Users\Application Data\Blender Foundation\Blender\2.57\

Linux: /usr/share/blender/2.57/
or
$HOME/.blender/2.57/

Another way would be to do a search for ‘startup.blend’.