Replaced drive D, with new 320GB (serial) hard disk. Cloned drive C (250GB) to new 320GB drive (D). Upon completion of cloning, moved 320GB (D) to C, and placed orginal disk back in drive D. Rebooted system and found drive D (the drive removed from the system before cloning) was not accesssible. Formatted drive D, and checked with Western Digital data lifeguard tools and found no defects, however, the drive still is not accessible. The drive was accessible before cloning.