After a reformat and MBR rebuild, I doubt that the RAID data is still on it. You could always download and boot the Parted Magic toolkit and do a Secure Erase, which tells the drive to completely reset itself.
You could download the diagnostics from WD and test the drive; it may simply be defective.
It is remotely possible that the problem is in other hardware. Have you ever had that particular machine run with Win7 on some other disk?