I was running a duel boot windows 8.1 and ubuntu 14.04 when I suddenly could no longer boot my system. After booting into a live usb and run GParted I get this error:
Input/output error during read on /dev/sdb
/dev/sda contains GPT signatures, indicating that it has a GPT table. However, it does not have a valid fake msdos partition table, as it should. Perhaps it was corrupted — possibly by a program that doesn't understand GPT partition tables. Or perhaps you deleted the GPT table, and are now using an msdos partition table. Is this a GPT partition table?
Both the primary and backup GPT tables are corrupt. Try making a fresh table, and using Parted's rescue feature to recover partitions.
Is there a way to fix this? I have tried TestDisk which won't run. Is there also a way I can backup my hard drive before I do anything that might damage my computer.