Your hard drive might appear clean but still be full of sensitive material that you did not want to download in the first place and it might very well be a Serious Criminal Offence to have that data stored on your computer even if you didn't know it was still there. You could go to Jail! Pressing 'Delete' or emptying your 'Recycle Bin' - or even 'Formatting' your disk - simply will not work, the sensitive material will still remain on your computer's hard drive! You may be held responsible for any data which you allow to remain on your computer, even if it was only by accident. Even File and Internet Searches you have made which you thought you had never "saved to disk" are recorded as permanent evidence on your computer's hard drive!