It was originally the system drive when prior to getting the M4. But that transition went smoothly, I've been running the m4 with the wd caviar as my storage drive for almost a yr now. I just formatted the m4 to reinstall windows and thats when the issues pop up.
My mobo is a Biostar 790gx. The WD shows up in the Bios but my M4 doesn't. In fact sometimes I can't even boot up properly, the M4 isn't recognized and on bootup my system says there is no OS installed. Not sure whats going on.