I want to securely erase my hard drive. I created a OS X Lion USB boot drive. I booted to the USB drive. I selected the option to start Disk Utility. So far I am doing this correctly, right? So then I select the hard drive "121.33 GB APPLE SSD TS..." from the window on the left. I go to the "Erase" tab. I can select a Format and Name for the selected hard drive and the Erase... button is pressable, but the Erase Free Space... and Security Options... buttons are greyed out. Why is this? I want to do the 7 pass erase to make sure that everything is gone. It's the same thing when I select the "Macintosh HD" partition name that is under the "121.33 GB APPLE SSD TS..." drive name. I can go to the "Erase" tab but the Security Options... button is greyed out. Only the Erase... button is available. What am I doing wrong? This is for a 2010 Macbook Air in case that matters.