<< I guess it took me a while to state the question correctly. 🙂 >>
You never stated the question correctly. You're asking for average filesize, which is very difficult to measure in any meaningful way. You would have to average out the file sizes on the hard drives of thousands of people from all walks of life. That would be a very difficult problem logistically.
What I gave you is how many hours of multimedia data the hard drive could hold if you created a single file in a specific format at a specific bitrate to fill up the entire drive.
Depending on the intelligence of the audience, you can rephrase the results.
Rather than saying 40,000 minutes of 128kbps mp3 music, you could say "almost a month of near-CD quality music".
Rather than saying 5183 minutes of DivX (which is the number I actually got), you could say "3 and a half days of near-DVD quality video".
In order to do the same thing for text, you will have to figure out how many kilobytes of ASCII text contitutes a "page", which I'm really not interested in working out.