USB Device Not Recognised / Unknown Device


we have two WD My Passport 320GB hard drives that both have the same issue. We use them as backup drives for our HP ML350 server with Small Business Server 2008. They have been upgraded to the latest firmare and the software removed.

Occasionally when they are swapped over the appear as USB not recognised. At first i thought it was the cable into the HDD as it seems very loose but i now look out for that. It seems to happen randomly and can normally be fixed by plugging the drive into the front usb if it was in the back or vice versa.

Why is this problem happening? Is it power issues? BIOS/Mothboard issue? Cable issue?

My next thought is to glue the cable into the external hard drive so i know its not an issue with that coming loose.

Thanks in advance

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I am having the exact same issue.

I have 3 WD 1TB Elements USB external HDD’s.

Server 2008 Enterprise.

The drive are optimized for quick removal.

Sometimes the drive(s) just are not recognized and do not get an assigned drive letter.

If I reboot the server then it fixes the issue.

When this happens -

I can see the drive in the device manager.

I can also see it in the “safely remove hardware” utility.

I cannot see the device or volume in the disk management console.

You cannot get the drive to mount until a reboot although the other 2 may work fine.

I called Western Digital and they told me the drive I had was not designed for Server 2008 so there was nothing they could do.

Any help would be appreciated.


Hi CoderXMan,

my problem is not quiet the same i dont think. When i plug my drive in it shows in device manager as ‘Unknown Device’ and I dont have the option to remove it via the Remove Hardware Utility.

I have not tried rebooting as it is the main server and downtime is critical, but when the issue occurs usually one of the following fixes it:

  1. Unplug, leave for 10 minutes and plug back into a different USB

  2. Move from the back USB’s to the Front USB’s

  3. Plug a different drive in, remove it, and the original.

Thanks in advance