WD Hard drive 3709A is not recognised on my computer

SOURCE: Wd 120gb External no longer recognised by my PC

It stile does not work

SOURCE: my computer will and won't reconise my WD My Book but not both drives

any answer?

SOURCE: WD 500g hard drive computer cant read it

Is your hard drive power-up?
Do you hear your hard drive just spinning?

If so, your PCB may went bad. If you hear the hard drive clicking then your PCB or the heads went bad. If you need the data, you might have to ask the data recovery guys to get them back for you or find the PCB on Ebay.

If you don't care about your data, send it back for the warranty replacement

SOURCE: Flashing blue light on external WD hard drive & not recognised

sounds like you are using the wrong power supply. Check the amp output on the power plug you plug into the wall make sure its the same as the amp input of your external harddrive

SOURCE: my wd portable hard drive isn't being recognised by the computer

See below from Western Digital:

Try the following steps to see if the drive comes up:

1. Power off the computer all the way.
2. Unplug the data and power cables from the back of the drive, and then turn the computer back on.
3. Attach one end of the power cable directly to the drive and the other end into a wall outlet. Wait a couple seconds for the drive to do its internal test, then move to the next step.
   Note: If you have a Passport or an Elements portable drive, they do not require a power adapter. Skip steps 3 and 4, and proceed to step 5.
   
4. If the drive has a power button on the back or front, press it to power the unit on. The lights on the drive should illuminate and after a few seconds go solid. If the lights move a little, that is normal.
5. Make sure that the computer is powered up, and the desktop is fully loaded, then connect the drive directly to the computer and see if it is detected.

If the drive works on another computer, then the problem most likely lies with the computer system you started with. Make sure that you have the latest driver updates and Service Packs for your Windows. If the drive is still not recognized, then you will most likely need to contact Microsoft or the computer manufacturer to see if they can assist you.
If the drive doesn't work on another computer, even after changing the data cable, then it sounds like the problem could be with the drive, itself. Check Disk Management and see if the drive is recognized in the lower right pane. If so, you may need to partition or format the drive in order for it to be recognized. If the drive doesn't show up in Disk Management, then the drive has most likely failed and will need to be replaced. Please see the links below for additional information.

Important: You do not want to partition or format the drive if there is data on the unit that you need. In order to retrieve the information on the unit, you may need to contact a data recovery company to see if they can help you retrieve the data.