Unknown Device message for a USB External Hard Drive..supposed to be plug and play

Hi mgregurich,

I would suggest you to try the following steps:

Step 1: Check for the error code in the device manager

1. Open Device Manager by clicking the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking Device Manager. 

 If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

2.   In Device Manager, locate the USB device and then double-click the device name.

3.   under the general tab look for the device status for any error code listed.

http://windows.microsoft.com/en-us/windows-vista/Get-help-with-Device-Manager-errors

Step 2: Run the fixit provided in the link below.http://windows.microsoft.com/en-US/windows-vista/Tips-for-solving-problems-with-USB-devices

Step 3:  Unplug the power and USB (universal serial bus) cables, wait for some time and plug the external hard drive to another USB port and check.

Also connect the external hard drive to another computer and test if it works fine.

If the issue persists,

Step 4: Reinstall USB controllers.

 First, please disconnect all USB devices and then perform the following steps:

1.   Click "Start", type in Device Manager the Search bar and press "Enter". Click Continue if necessary.

2.   In Device Manager, double click to expand "Universal Serial Bus controllers", right click on the "Host Controller", click "Uninstall" and click "OK".

3.    Repeat the step 2 to uninstall all items under "Universal Serial Bus controllers".

Then, restart your computer and windows vista will reinstall all USB controllers automatically.

If the issue still persists, you may contact western digital for more help.

http://support.wdc.com/

Thanks and Regards:

Ajay K

Microsoft Answers Support Engineer

Visit our Microsoft Answers Feedback Forum and let us know what you think.