HDD not recognized after changing drive Letter

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HDD not recognized after changing drive Letter

I changed the drive letter of an external 2.5' HDD (from F to D).

Then for some reason I suddenly can't use the drive anymore.

Now when I plug it, the error message is on Win7 is "You need to format the disk in drive"
The error on Win XP is D:\ is not accessible

which is quite weird.

The drive is not used much, it never had surface problems, etc.
Of course I don't want to format it because I have some info there.

Any ideas about what the problem could be...?

Clarifications Clarifications
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Who Am I Really
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only reserved drive letters are ones already in use

you can't change the drive letter in disk management to one that is already in use

on a system with no CD/DVD drive, card reader, or floppy drive that has windows installed on the default C:\
you can assign A:\, B:\, or any letter from D:\ - Z:\ to any other partition / drive / mass storage device
windows assigns the letters sequentially after C:\
thus you generally won't encounter a USB drive getting A:\ or B:\
but if you plug in 23 storage devices you will have used all the letters from D:\ -> Z:\,
and then when you plug in number 24 you will get a drive letter assignment of either A:\ or B:\

in this case however, I agree with Col
and I'm leaning more to either the corrupt partition table or a mechanical or electronic/electrical failure of the HDD or USB -> SATA/IDE chip(s) etc. in the enclosure
removing it from the USB enclosure and attaching the HDD directly to an internal connector or a known working USB adapter will give some idea about whether or not the electronics are fried in the enclosure or if the HDD has gone for a dump,

I've seen these things just go poof for no apparent reason

recently had an HDD go poof just by touching the case while it was writing
heard a click and then it was gone, (the read / write heads were immediately barbecued)
I know it was static because of the dusty & dry environmental conditions in that particular office, but I didn't even feel it leave my finger

a static blast up the USB cable while plugging, unplugging or just grabbing it can cook these devices.
even a small static blast that you might not even feel can cook toast it
a larger static blast can **** a whole trace line right out of a PCB

Removing a USB SD card reader, flash drive, or HDD without safe removal can toast the partition table,
however, even with safe removal you can still fry it electrically with static discharge

There's more than one way for these things to go poof.

if it's a partition table corruption
there are some tools available that can correct the partition table or attempt to read the data from the disk that appears as unformatted

but an electronic / electrical failure will require data recovery services

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@Who Am I Really
I have two objections to your post.

Static electricity
You are exaggerating the dangers of static electricity.

Do you not think that the designers of the actual disk drives have not worked hard to resist static electricity.

Yes external drives will just fail. They are commodity products, mass produced, always seeking lowest cost to manufacture. Cooling is often marginal. Time and heat (added by dust) take their toll. Components weaken. One day the surge of power up becomes too much and a component fails.
These fail on power up have led to the debate between "never power off" and "power off when done"
Is static electricity the great destroyer of external drives. I don't think so.

Safely Remove is not needed
The requirement to use "safely remove" is incorrect old advice.
External drives, by default have write caching disabled.
Once a few seconds have passed after the last activity the drive can just be unplugged.

In order to see the setting...
In windows explorer right click the drive -> properties -> Hardware (tab) -> in the list select the disk and click Properties -> Change settings -> Policies (tab) -> and you will see...

Removal Policy
(*) Quick removal (default)
Disables write caching on the device and in Windows, but you can disconnect the device safely without using the Safely Remove Hardware notification icon.

This is the default even for external disks that are NTFS formatted

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OH Smeg
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but you can disconnect the device safely without using the Safely Remove Hardware notification icon.

That is your mistake you Can Not Safely do what you are suggesting without running the risk of corrupting the Partition Tables on the HDD itself.

When you remove the plug all you are doing is removing the power and leaving the HDD to it's own devices to park it's Read Write Heads and stop immediately what ever it was doing. If it was performing a Write to the drive no power means that the Write is incomplete and possibly the Read Write Heads could have touched the Platters damaging the Heads and the platters in the process.

While you may get away with just pulling the USB Plug 99 times out of 100 it's going to eventually come and bite you on the Backside and trash your data which is what I think you'll find has happened here.


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I'm fairly certain you cannot damage NTFS that way.
But Fat32 (which it seems flash drives are still formatted too), definitely could damage it.

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The point of my advice was to do some first-step basic trouble shooting.
Trying the disk on another computer would have been another first step.
Evaluate, diagnose, remediate.

What would you have advised ?

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Sorry if I came across as snarky Cmd_Line_Dino. That wasn't my intention. I have a lot of respect for the people that give up their time to help out others on these forums, and I don't want to discourage you from doing so.

I did actually write another post about what I thought the issue was but it didn't save for some reason (happens to me sometimes... I think it's a problem with my laptop, it badly needs a reformat). As others have said, it is corruption; perhaps a physical fault, or perhaps from yanking the drive out without first safely removing it. Whatever the case Windows can clearly see the drive and recignizes it as being a hard drive, but it cannot make sense of the file system so offers to format it. A thorough chkdsk might fix the problem, or using a tool like TestDisk to repair the partition table might also do the trick.

I do need to point out that Safely Remove Hardware is still needed and it is dangerous advice to suggest otherwise. Sure, 99% of the time you will get away with doing it provided you wait 30 seconds after you *think* the computer has finished using it. That other 1% is the problem; that's where problems like the OP's come from. (Personally I'm lazy and yank my drives ut 90% of the time. I always safely removeh drives that have data I really care about though).

The reason you need to safely remove (even if you have optimised for quick removal turned on) is that the drive will often be accessed in the background. Anti-virus systems and poorly written shell extensions that don't close handles are the two worst offenders for this in my experience.

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About using safely remove
So we should believe you rather than Microsoft ?
On there website MS CONTINUES to say it's not needed.
I will go with MS considering their decades of experience dealing with a vast universe of hardware.
But of course, as MS says, don't pull the cable while there is activity.

And why do you and others here keep saying the partition tables will be damaged.
First, for the vast majority of systems it's partition table (singular).
Second, for those systems it's a single 512 byte sector on the disk which is NEVER changed UNLESS you are reconfiguring the partitions on the disk.
Just because it's sector 0 is that why you think it's going to be changed/corrupted ?

About power being abruptly removed from an active hard disk
Disk drives are DESIGNED TO DEAL with the unexpected loss of power.
They immediately park the heads in the landing zone. Some use the rotating spindle to generate power to do the last activity and parking.
Think about how each day around the world hundreds of thousands of systems either abruptly lose power or are just powered off with no use of system shutdown. And for the vast vast majority nothing happens.

And about USB (AGAIN)
Here too, USB is designed for plug/unplug with the power on.
And here is a tidbit. In XP doing safely remove would drop the USB power.
Starting with Vista safely remove no longer drops the USB power.
Perhaps an evil MS plot to destroy USB devices ... nah probably not.

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I don't even see the safely remove anymore.

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HAL 9000 Moderator
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Feel free to believe what you want to it personally doesn't worry me in the slightest.

I will however mention that I make a lot of money by recovering lost data on external HDD that people have corrupted the Partition Table as you seem to prefer

I didn't say that it happens with SSD Drives or things with no movable parts but it most defiantly happens with mechanical HDD. I currently have a 2 TB Drive from a customer which is unreadable and they want their data back off it. Easy Money when the customer does stupid things. :^0


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The HDD is SATA; I can't rename it back because the computer doesn't see it, even in Disk Management. There's no drive assigned with letter D.
Of course, any HDD can fail, but this problem coincided with changing the drive letter, so it's quite a low probability that the cause is different.