The partition was bootable, but it's not anymore. I booted with an ubuntu live CD.
"fdisk /dev/sda3 -l" shows this:
Disk /dev/sda3: 626.4 GB, 626396585984 bytes
255 heads, 63 sectors/track, 76155 cylinders, total 1223430832 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x6e697373
This doesn't look like a partition table
Probably you selected the wrong device.
Device Boot Start End Blocks Id System
/dev/sda3p1 ? 1936269394 3772285809 918008208 4f QNX4.x 3rd part
/dev/sda3p2 ? 1917848077 2462285169 272218546+ 73 Unknown
/dev/sda3p3 ? 1818575915 2362751050 272087568 2b Unknown
/dev/sda3p4 ? 2844524554 2844579527 27487 61 SpeedStor
Partition table entries are not in disk order
Any advice on how could I address the issue? I would like to rescue the whole disk if possible.