I've decided to do a fresh install of Mountain Lion on my MacBook Pro (using a USB flash drive with the install disk on it). My only concern is my harddrive has been encrypted using Filevault 2. Will this pose any issues? My plan was to boot into the USB drive then format the internal HD using Disk Utility, just as I always have when previously doing fresh installs. Do I need to decrypt the disk first? Any help or advice will be greatly appreciated.