+ 0 Votes You don't mention external disk type Cmd_Line_Dino Updated - February 1, 2013 at 2:54am PST Is it USB or eSATA or something else ? On power up does the drive spin up and do the usual few seconds of activity ? Is the use of conflicting with a CD/DVD/Blueray drive or chip reader or something. On the Win 7 system... Disconnect the problem disk and reboot Run DISKMGMT.MSC. Is some device assigned to ? Be sure to look through the lower pane list. CD, DVD etc appear only there. If there is a then change it to some other letter. Connect the problem drive. Is it visible at all in DISKMGMT.MSC Try a power cycle reboot.