I bought a Western Digital hard drive last June. I mainly use it to store files and pictures, but don't put many programs on it. A few weeks ago, while trying to open a file, I received an error message. When I rebooted my computer, it showed the drive was completely blank and unformatted. I think it's a physical problem with the drive, and not virus or software related.
In other words the exact same thing happened to you? You lost everything and for no logical reason. Please note my drive is Western Digital too.
I've seen cases where the hard drive's controller died, but often it's just the MFT getting corrupted. It's pretty rare (for me one time in five years of NTFS usage), but it does happen.