Using HDT to format a drive that has been previously formatted with ExpressPro-Tools (EPT) may cause an error. This has to do with the drive automatically loading the ATTO driver in to RAM. To reinitialize an ATTO EPT drive with HDT, launch EPT, use Erase Disk to wipe out the directory and drivers on the ATTO drive. Restart the computer -- this will purge the ATTO driver from RAM. Then, launch HDT and initialize the drive (which will not appear on the desktop at reboot since it has no driver). This particular issue -- HDT not being able to initialize an ATTO EPT drive -- is not dependent on the presence or absence of the ATTO extension.