Having issues with doing a clean install of Lion. Followed all the guides, but it doesn't seem to be working out for me. I've burned Lion on to a disk. Guides tell me I should go to Disk Utility and erase my HD, well I can't, ERASE is greyed out so I can't click on it. So not sure what to do, what I'm wanting to do is totally erase my HD, and do a clean install of Lion from the disk.. Any help? Help?