If other drives have a letter but the external is missing then you can right-click and select change drive letter or path. Seagate external hard drive is always used to back up important data or transfer data between computers. Visit the Warranty and Replacements section on Seagate.com for further details. Click Add then assign a letter and OK. Drive not detected troubleshooting: If it is missing, verify that other drives have a letter. This article has the most comprehensive solutions to Seagate internal and external hard drive not working problems on both Windows and Mac. When your Seagate hard drive not working, it is usually about external hard disk not detected, not recognized, or not showing up. The following are some solutions to solve "Seagate external hard drive not showing up or detected". If you see Code 28 (this may work for others codes too, ie Code 43) then try the following: Close the window with the code. If you do not need the data and the drive is still within warranty, you will want to have the drive replaced. 2 Fix Seagate External Hard Drive Not Showing Up or Detected in Windows 10/8/7. So, it's essential to make it works fine all the time. Drive letter - Verify that the drive has a drive letter.