Please note: This answer is highly recommended prior to returning the drive for a replacement.
Some of the simple troubleshooting techniques used below can be applied to external hard drives on a Mac as well as a PC.
I was using my external hard drive for some time and now a drive letter (icon) does not appear in My Computer (Mac Desktop) and I cannot access the data on that drive.
there could be a few reasons why the drive is not showing up in My Computer (Mac Desktop). The drive itself could have failed, the partition on the drive may be damaged, the data cable may no longer be good, or the drive may no longer be getting enough power to fully spin up.
It’s always best to start with the most simple possible causes when troubleshooting. Follow the steps below in order to eliminate the common simple issues:
- If the drive is not being recognized, disconnect the power adapter from the surge protector/UPS and plug directly into the wall. Sometimes, surge protectors diminish the power being supplied as more devices are added to them.Note: If after doing this the drive does not spin up at all (you can tell by feeling for vibration on the drive), then either the drive or the power adapter has failed. You will need to replace the power adapter to proceed with the troubleshooting. If after replacing the power adapter, the drive still doesn’t spin up, then you will need to replace the drive. You will find links for data recovery and warranty replacement down below.
- If the drive is spinning but not recognized in My Computer (Mac Desktop), then change out the data cable with one that you know is good. Cables get old and the wires inside can break, or pull loose from the connectors.
- If that doesn’t work, connect the external drive to another USB port. The USB port could be malfunctioning.
- If your drive still isn’t being recognized, turn your PC (Mac) off, disconnect the data cable, restart the computer, and once the operating system is fully up and running, reconnect the data cable. Give it a minute or two to recognize then you will want to access Disk Management (Disk Utility) to see if the drive shows up in there. If it does show up in Disk Management (Disk Utility), then you have a corrupted or damaged partition and will need to re-partition and reformat the drive for it to be recognized on your PC (Mac). See Links and note below.
- For help with accessing Disk Management, or reformatting your drive in Windows, see How to install, partition, format, or reformat a WD external hard drive in Windows XP.
- For help with accessing Disk Utility, or reformatting your drive in Mac, see How to partition, format, or reformat an internal or external drive on Mac OS X 10.4.
Important: If you have data on the drive that you need, do not reformat the drive. You will need to perform data recovery on the drive, before you can proceed with reformatting the drive. With a damaged partition, there is data recovery software that may restore the data. You can research the various kinds on the internet.
- If the drive doesn’t show up in Disk Management (Disk Utility), then the last option you have is to connect the drive to another PC. If it works, then there’s an issue with either the hardware or drivers on the primary PC. You will then have to troubleshoot that computer and operating system. For help with the operating system, you will need to contact either Microsoft Support, or if you have a Mac then Apple. For help with the computer hardware, you will need to contact the computer manufacturer.
- If the external drive does not show up on another PC, then the drive has failed. You will need to go to data recovery if you need the data on the drive. If the drive is under warranty, you can then replace it with them.
Final Note: (For Windows) If the computer does detect the drive, you can test the drive to make sure that there won’t be any ongoing issues by using Windows Data Lifeguard Diagnostics. (For Mac’s): You can test the drive by running First Aid.
If the software reports any errors for the drive, please see Data Lifeguard Tools 11 Error Codes for a list of error codes and what they mean.
IMPORTANT: To avoid corrupting or losing the data on your external hard drive you should always shut down the drive correctly before you disconnect the data cable from the drive or computer, or the power connection from the drive or the wall outlet.