Troubleshoot: Windows won't recognize USB hard drive / fix unassigned drive letter

Sure sounds like a USB driver or filter issue. Have you tried these yet?
See How to Cleanup and Remove old USB Storage Drivers
See CD/DVD or Disk Problems? How to Fix Problems Caused by Filters

Thank you, you fixed my problem

Dear LookinAround
Thank you so much for your assistance - your step-by-step instructions on how to use Drivecleanup.exe worked perfectly and I can now access my Iomega external hard drive in Windows again! When I downloaded the software and ran it last night, prior to posting on this board, I read the accompanying text file but nowhere did it instruct me to place the file in the Windows/System32 folder, nor to run it under an elevated command prompt. I apologise for being such a noob and really appreciate your help in fixing this problem, which was driving me nuts.
What a great forum this is.

Hi Pachacuti

Thanks for updating us with the good news! And glad to help

The Remedy Works Short-Term

My inability to view USB hard drive contents was resolved by" "Rt click My Computer>Manage>Disk Management" shown on this thread. I did so by right clicking the unidentified USB drive that was shown in the Disk Management window and assigning it a unique drive letter. I assigned it "H" which left a gap between "E" and "G" for Win 7 to assign to other USB devices on a temporary basis. Unfortunately, this was only a temporary solution, as Win 7 does not retain it as a permanent assignment after dismounting that specific device.

Is there another way to permanently dedicate a drive letter assignment to a specific USB device, so that it will use the dedicated drive letter each time that it is mounted? My XP computer does retain dedicated drive letter assignments for USB devices that is repetitively mounted and dismounted.

@bobcinreno

Windows 7 should automount the USB drive just as XP does. If you can mount it manually, like you did, it may be a sign of a drive letter conflict. Did you also try removing old USB storage drivers? How to Cleanup and Remove old USB Storage Drivers

Corsair voyager 32gb usb 3.0

my USB which i have bought from amazon site stopped working and the format command of win xp sp3 gave me this message ( there is no device ) and HP USB Disk Storage Format Tool gave me no media in the specified device { the name has changed into Innostor NAND 1.00 (0 MB) what should I do I live in Jordan and the idea of returning it is little bit frustrating and cost a lot
please contact me using my e-mail address

Thanks so much for these tips! I've been trying to figure this out for days and keep going in circles. None of my usb flash drives will open on my new Lenovo laptop unless I go into safemode. Then, only the ones connected while in safe mode will open when I restart but if I shut down the system I'm right back at square one. I know its not the flash drives because they open fine on my desktop. I'm really hoping I don't have to restore to factory default since I can't use my usb external hd all my other back ups are on. I haven't tried it yet but I'm pretty sure that's when my issues started. The first time I backed it up it ran fine but I hadn't connected the base and later learned I had it in the lowest powered port. Since then my external hd won't do anything with I try to do a back up AND I have to go through this huge ordeal when I want to open files from a usb drive. All my other usb devices work fine, it seems to be isolated to storage devices.

I guess I'm just going to go down your list of fixes and if that doesn't work I'll have to do a system restore. I must say that I'm not very happy that I didn't get my own OS discs with my new computer. Its partitioned on my hard drive which I think is extremely careless. If I own the key why not just give me the disc? Maybe its just me but I've never had so many issues with a brand new computer. I'm a student and really need to fix this issue before classes start in the next week. Internet explorer crashes a lot as well so I don't know if that's related but I've never really liked IE anyway.

Thanks so much for the info, if you have any suggestions please let me know.