[ubuntu] Suddenly, I Lost half of my hard disk partitons

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http://ubuntuforums.org – Hello, I lost half of my hard disk partitions like 275 Gb from my 500 Gb HDD i was running Ubuntu 12.04 x64 + windows 7 pro x64, after losing the partition i lost the access to each of the operating system even that i was still have the windows 7 partition i did a fix to the grub by using boot repair and nothing happened still have this msg "Multiple partitions". Now i want to know if it's possible to recover that big lost even some of it and if not so how can i rebuild my partitions again by using ubuntu or linux. (Hardware)