Are you using the latest version of Hard Disk Sentinel? If so, then it looks like your hard drive has bad sectors. As it says, it's either the disk surface or the read/write heads. I strongly recommend that you backup any important data.
If you're not using the latest version, then install it and check it again.
I just did a huge reformat and actually went into OS X (on PC) and disconnected and reconnected the dive (which I hadn't done so) and seems to be working correctly now as it does no longer give me an error when booting OS X, once I install Windows 8 again I'll check to see if it was the cables that were incorrectly connected.