My external hard drive wont conect to my computer.

hello

do this and it should work : unplug the power and USB cords from the external WD drive

wait 20 seconds. plug the power cord into the drive (make sure the other end is plugged into the wall)
wait 20 seconds, plug the one end of the USB into the computer, and the other end into the WD external drive.

in a few seconds, your computer should see and activate the WD external drive.

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That needs a motherboard drivers upgrade.

What happens is that the BIOS starts detecting and checking booting devices.

Earlier motherboards are not able to detect external hard drives and boot from them.

So the solution to this is to turn off the computer and then disconnect the cable.

Remove safely the HD and then restart.

God Bless You!

Working previously is good.
Ok, a quick list of the things i have done wrong in just this circumstance.

Is the power supply plugged in and switched on?
Is it supplying power?
Is it supplying the correct voltage?
*Note: You will need a multimeter to do this. 12 Volts is the correct voltage.
Is the power supply plugged into the drive? All the way?
Is there a power switch on the drive? Is it in the on position?
Is the data connection plugged in? All the way? The computer end also? All the way?
Does the cable run from the computer to the drive, or are there other cables lying around two of which are plugged in at one end?
Are you using the same data cable you did before?
Does it work with different cable?
*A caution here. Not all cables are equal. You want to use a USB 2.0 cable.

If it was working before, any one of those could be the problem. I've had them all.

first of all , you are looking at the wrong voltages. The important voltage is the DC OUTPUT, which is the voltage the external harddrives use AND the polarity of the plug attached to the harddrive end of the cable.
if both the harddrives have say 12v dc output and both have the insignia of the center conductor being + (posative) then you can interchange them. and you CAN run a 9volt unit with 12volt DC power, but not the other way around.
Look at your power adaptors again for the OUTPUT and polarity.
should be a half-circle with lines depicting the polarity(+,-) of the center and sheild connections to the hard drives printed on both the harddrives and the power adaptors . This can also be tested with a dc volt meter while the adaptors are plugged into the wall.
DO NOT try to test the AC end while plugged in!!
Regards

Yes it is a hard drive. You have to plug a usb in the hard drive and one or 2 usb plugs in the computer to make it work.

You will need a cable that has on one end one usb connector and at the other end one or two usb connectors. My advice is to have 2 usb connectors at the other end, so the device could work properly.

If you need further assistance, post a comment.
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1. The usb cable could be defective

2. The usb port could be malfunctioning

3. The drive could be defective.

Try using another usb port, or try adding a PCI card usb ports

if it came with a driver disk or an install disk then try running that before hooking up your harddrive

Does the drive have a socket for external power?  or do you have a USB cable with 2 usb and 1 mini usb?
Sounds like it needs external power.

Try a replacement USB cable first. If that does not fix the problem, then the USB to SATA adapter board is faulty, in that case you will need to take out the internal disk to replace the external enclosure.

see
YouTube - How To: Take Apart A Western Digital My Book Enclosure

If unit is under warranty see : WD Support > Warranty Services > End User > Warranty Policy.

Note any SATA external enclosure willl work wthe same with the internal WD HD.

if u are using a external hard disk case with the normal hard disk
try connecting your hard disk with a new casing.
if it is made as a external hard disk change the cable .
because after a few time usage the cable will not be quite good as new.
After inserting the usb cable in your pc if it shows any warning
information, or any message just give me that too for exact solution