Before computer installed Windows 7 and ubunt, through the guidance of grub launched, but the day before yesterday the silly reinstall Windows 7 (only the c disk),,,,,,,, crashed, and then turned on, and real grub rescue, by ls and the set command to reboot, or can't get into the system (there will be a system in the options menu), at the same time also can't get into PE,,, big hand to solve,