There are a couple of ways.
If you can read as fast as the symbols going by your eyes when you use the matrix like screen saver then just use this:
ls -SR /
That breaks down to ls (list) -S (put in order by the file size) R (recursive, it follows the subdirectories)
All you have to do is add an "lh" in between the SR and you will get the file size in human readable format.
This will scream by, at a mind numbing pace, so I would pipe it to a file. The entire way that I would recommend is as follows:
ls -SlhR / > biglistoffiles.txt
Good luck, and may the penguin be with you.