I let one of my ex-friends borrow my Powerbook for a video he did a while ago. I got it back with some really sutty url's in my history. Some of them worse than the others. Anyways me and my mom and pretty much everyone else I know who uses mac cannot figure out how to completely destroy the sick shit he looked at. I take this book to school and soon I will be taking it back to work, Is there anyway we can get rid of the stuff perminantly?