How do I get disk usage information on my 'Machintosh HD' icon on my desktop?
I did it on my old computer, so I know it's possible, but can't seem to find the option again.
I am on MacOSX 10.8.2.
Right-click a blank location (e.g. not on an icon) on your desktop and click 'Show View Options'.
Check the 'Show item info' box:
The effect happens immediately.