How much did your computer cost? $1000? $2000? How about your internet, maybe $30 per month?
Now count your MP3s... or better yet, count the number of artists. CDs usually have one artist on them, and usually have 10-20 songs on them. Take the number of atrists of the songs you've downloaded, add a few if you have more than 20 for an artist, since you'd buy 3 or so CDs anyway for so many songs, and subtract the number of CDs you've actually bought. Multiply that number by a common CD price... say $20.
Now add up all the games and software you've downloaded but haven't bought and total it with your MP3 total.
Pay for your computer yet? It would be an interesting poll... but i cant create one
I suppose you could subtract what you wouldn't have bought anyway (Photoshop?)