Boot Repair Disk
Boot Repair Disk is an open source rescue disk which can fix many common Windows and Linux boot problems (boot sector, master boot record, GRUB, more).
While this can be a horribly complex area, Boot Repair keeps everything very simple. We chose to run a 64-bit session, selected a language, and waited for a while as our system was checked. A dialog then appeared with a “Recommended repair” button, and clicking this should fix the most common problems.