First make sure that it's a compatible drive (i.e. Oxford 911 chipset and 7200 RPM or faster spindle speed).Secondly, make sure that Apple's Drive Setup was used to format the drive. If the drive mounts on the desktop, simply highlight it and choose Erase Disk under the Special Menu.Lastly, if there was software installed that came with the drive (i.e. Hard Disk Speed Tools), remove the software and disable the extensions associated with the software.