External Hard Drive not recognised

By Mred215 ·
I have been using an external hard drive for about a year now with no problems. Over the past couple of days however, I cannot get it to appear on my computer. In fact the drive won't even spin up when connected to my PC.

I have tried the drive on another computer and it works fine, but when I plug it in to mine it does nothing.

I have tried other devices in to the same USB ports on my PC and they work fine.

I am running XP SP3, and the hard drive is connected via USB. I have checked USB controllers in device manager and there are no errors, but I have updated the drivers anyway, but no improvement. Please help. :)

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Try this

by Jacky Howe In reply to External Hard Drive not r ...

Write down all fixed Disk and CD/DVD drive letters so as not to delete them. DO NOT delete any of the fixed hard disk drives or CD/DVD optical drives registry values.

1. Login with Administrative privileges.

2. Disconnect all USB or FireWire storage devices.

3. Open Registry Editor by typing regedt32 in the Run box and navigate to the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

4. Under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices there will be registry keys with the name that resembles the format of \DosDevice\X: where X can be any alphabet letter which corresponding to your physical system drive letter.

5. Delete all possible USB drives, FireWire drives and external drives which have a drive letter.

<b>DO NOT delete any of the fixed Hard Disk Drives or CD/DVD optical drives registry values.</b>

Exclude \DosDevice\A: which normally reserved for floppy disk drives.

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No Change

by Mred215 In reply to Try this

I deleted the USB drives and have rebooted. Tried connecting my external hard drives but still not opening. The PC still makes the sound as if something has been connected, but nothing other than that.

I have put a USB memory stick in to one of the ports and that is working fine.

I am looking at reinstalling Windows but need the external drives connected to get my files off it first. Any other ideas?

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Another idea

by Jacky Howe In reply to No Change

Try reconnecting back to your PC that it is working on and turn off system restore on the drive.

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OK what type of Enclosure is this?

by OH Smeg Moderator In reply to External Hard Drive not r ...

Does it have it's own Power Adapter or does it get it's power from the USB Port?

If it gets power from the USB Port try it in another USB Port on the computer where it doesn't work. Ideally one in a different connector to the one which it isn't working in.

If you do not have another USB Port that you can use get yourself a Powered USB Hub like the one shown here


And then see if it works now. I'm guessing that it will work and that your issue is related to the available Power not being sufficient to power this device.

What can happen is that when a USB Port is overloaded it can burn out the 5 V Supply to the Socket and stop working.

If the Drive inside the enclosure is bigger than 80 GIG and doesn't have it's own Power Supply you should be using 2 USB Plugs on a Supplied Y Cable at the computer to get enough power to run the Drive.

USB Ports Standard specifies 500 Milli Amps at the Socket but this doesn't need to be followed by the Computer/M'Board Makers and they could be supplying less or just have crappy Power Regulators on the M'Board which have gone off and are no longer providing sufficient Power/Current to run the HDD.

If this HDD Enclosure has it's own Power Supply make sure that it is actually plugged into a working Mains Socket.


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by Mred215 In reply to OK what type of Enclosure ...

Hey Col,

Well I had tried a different power supply this morning, as I have 2 external drives of the same make and model. There was no action with either drive on my PC this morning.

However, after reading your comment I thought I would give it another go. Turns out that both drives work, but only on one power supply. Both power supplies have the converter that shows a green light, but only one does the trick. Weird.


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Your Welcome. < NT >

by OH Smeg Moderator In reply to Thanks

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