Mystery Memory problem

I recently had a massive jump in the amount of full memory the finder says my hard drive contains. When I highlight the the individual hardrive and desktop icons and click "get info" the amount of memory doesn't nearly add up to the amount it says I have. I recently made some mix CDs and extracted 75 songs or so to Aiff from MP3s in Jam. Could it be that there is a massive cache stored somewhere that contains all this discarded info? I know I don't have 35 gigs of stuff on my comptuer.