Some Mac models use "Cable Select" instead of "Master/Slave" select. Possibly also true of 3rd party controller boards. In Master/Slave you have to jumper one drive as Master and the other as Slave. In Cable Select BOTH drives are jumpered for Cable Select... Could this be the problem? See for example: "Power Mac G4 (Mirrored Drive Doors) and (QuickSilver 2002) Education Model: About Cable Select and Adding Third-Party Drives" <http://docs.info.apple.com/article.html?artnum=86150> versus "Power Mac G4: Installing Internal Storage Devices" <http://docs.info.apple.com/article.html?artnum=31292> HTH -- Garth Fletcher