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I am attempting to connect a Lacie USB external hard drive to a laptop with Windows XP SP3. It appears fine in Disk Management with an Active and Healthy partition but it does not have a drive letter.

If I assign a drive letter I can view the files by opening the partition from Disk Management. I can also access the drive from the Command Prompt. However, the partition does not appear in the Explorer, unless I log out and back in. Unfortunately, if I restart the computer the partition comes back without a drive letter again.

I've tried removing all the USB devices in the Device Manager and then reinstalling but the problem remains. I've also tried connecting to a different USB port. I have not yet tried attaching the drive to another computer.

What else should I try?

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before you try anything, backup the files on that drive while you still have access. – Molly7244 Sep 7 '09 at 0:30
I've seen similar behavior on a few machines (drive letter was assigned, but no program using Windows Shell - including Open File dialogs - would show the drive). It'd be cool to know what goes wrong there. – Ivan Vučica Sep 7 '09 at 1:12
up vote 3 down vote accepted

You may get some help in these USB Drive Troubleshooting notes.
The site has a lot of other USB Drive related notes and tools:
USB Drive Letter Manager is one of them.

You can also mount an external USB Drive as a 'Folder' on your windows system
(rather than allocate it a drive letter) -- some quick notes on that.

Some more notes also at HowToGeek: Find Your Missing USB Drive on Windows XP

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