Well, as i'm quite to my Mac OS X, i've been having problems and even thought of selling my laptop lol It's probably just me that doesn't know how to do stuff.
Anyway Corbab, file types? unwanted programmes e.g Google earth, Skype, Utorrent files, sound files, videos of up to 700mb.. that kinda stuff.
To delete, i click on the trash can icon and select 'Empty securely'. Even may have only 4 or 5 files, but when deleting starts, it shows me from 4000-35000 files.. going down one by one!!!!!!!!! I would probably be DEAD by the time trash can is emptied!