640 Gig HD not showing up/disapearing
When I boot up, all my harddrives show up, my 160 gig that my OS is on, my 320 for music and data files and my fairly new 640 gig for larger video files. The issue is with my 640 gig Western Digital drive, I can browse it, stream from it, move files around within it, but when I try to move files that are on another drive to the 640 for storage I get an error, the main portion of the error is "problem copying check location and try again" and the error also states that there may not be a disk present in that drive or that it may be an offline location and that the destination does not exist.
Most times upon reboot, the 640 shows up again (sometimes it doesn't show up at all), but alas, I still cannot move files to it. I ran Western Digital's harddrive diagnostic tools and it came up perfect, passing all tests. I unplugged the sata cable and moved it to another sata port on the motherboard, that didn't work either. I have windows 7, so there shouldn't be a size restriction within the OS. I can't hear any of the dreaded clicking sounds normally associated with a failing harddrive.
Any ideas or suggestions as to what the problem may be?