Intl. hard drive has disappeared from Windows Explorer whilst in use

@ layback bear ...
did the system specs via the auto route ... unfortunately, couldn't see the 'set info' button in the top left (or anywhere) on my system specs page in Seven Forums. it wouldn't let me copy & paste either so in the end, i just typed the data after running the SystemInfo.exe file.

@ jumanji ...
very little to report other than to say that i ran the 'CapacityRestore.exe' file in ordinary mode which worked fine. unfortunately, it didn't give me the result i wanted ... instead 'Hard drive is not accessible or damaged in some way. Therefore factory capacity cannot be recovered. Please try to run this program in another platform' appeared on screen.
i guess the only option left to me is to search around for a data recovery company unless there are other options that might solve my dilemma.

many thanks so far ... really much appreciated.

Exactly the same error message I mentioned in my post #8

"If the firmware corruption is reversible, your HDD capacity will be restored.

If the firmware corruption is irreversible you will get an error message something like this ""Hard drive is not accessible or damaged in some way. Therefore factory capacity cannot be recovered. Please try to run this program in another platform."

And so whatever firmware corruption has taken place ( I am still not sure that has happened, I shall come to that later :).) seems to be irreversible.

Now let us go by the book and see what happens. Download SeaTools for DOS (SeaToolsDOS223ALL .ISO) from SeaTools for DOS | Seagate burn it to a CD boot from it and run the tests. http://www.seagate.com/files/staticf...-dos-guide.pdf

In particular
F. Set Capacity
Occasionally, a disk drive may be too large and its size needs to be reduced to a lower capacity. Similarly, a drive with a reduced capacity may need to be reset to its native maximum capacity. Three choices are available under this section: Set 32GB Capacity. A common setting for older systems. Set Capacity to MAX Native. Full capacity is restored. Set Capacity Manually. Allows you to set a specific size.

Check whether it works.

( Instead of burning SeaTools for DOS on a CD you may also create a bootable pendrive with that ISO using Rufus https://rufus.akeo.ie/ and boot from it. Make sure that you do not have any data on the pen drive before using Rufus. Otherwise all data in the pendrive will be lost when Rufus formats the pendrive.)

I don't know if or where i've gone wrong somewhere but I've had a couple of problems in trying to download the SeaToolsDOS223ALL.ISO file. When I followed the link in your last post, the only active (possible) link to the file I could find was the 'download' button in step 4 but all this produced was the message "Bad Request: Your browser sent a request that this server could not understand".

I then did a search for the iso file from another source, downloaded & burnt it to a cd after which I re-booted the computer from the CD. It went well till the first window came up on screen asking me to agree or disagree with the agreement. The cursur was in the middle of the screen but I was unable to move it to the 'I agree' button using a number of different keyboard combinations and certainly the mouse couldn't shift it which I kind of guessed anyway.

So I was left with the last option, namely to follow the 'rufus' route. I downloaded v2.6 portable which seemed to d/l okay but 'Create a bootable disk using ...' was greyed out and I don't know how to un-grey it.

Any suggestions please?

Thank you for your reply. I ran the SeaTools for Windows programme for my 2000gig HD, the results of which are below.
They don't look good!!

-----------------------------
Now is a good time to make sure you have a current backup of your important data.

Unfortunately, your Seagate product has failed an important diagnostic test, possibly caused by problem sectors which are difficult to read. Seagate recommends that you run SeaTools for DOS, which has the ability to repair most problem sectors. SeaTools for DOS may be able to save you from the inconvenience and down time of exchanging the drive.

Suggest: SeaTools for DOS

Log Test:

-------------- SeaTools for Windows v1.4.0.2 ---------------
06/01/2016 13:24:04
Model Number: ST2000DM001
Serial Number: W1E1RRD2
Firmware Revision: CC24
Identify - Started 06/01/2016 13:24:04
Model Number: ST2000DM001
Serial Number: W1E1RRD2
Firmware Revision: CC24
Drive Capacity: 4.14 GB / 3.86 GiB
Max LBA: 8089949
Cache Size: ----
Power-On Hours: 0
Drive Temperature (C/F): 0 / 32
WWN: 5000C5005CCA0D1C
Sector size (Logical/Physical/Allignment): 512 / 512 / 0
Signal Speed (Max/Negotiated): 6.0 / ---- Gb/s
Transport Supported: SATA 3.0
Rotation rate: 7200 RPM
Form factor: ----
Specification Supported: ATA8-ACS
Encryption Support: Not Supported
Security Mode: Supported
SMART: Enabled
Host Protected Area features: Enabled
Advanced Power Management: Not Supported
Download Microcode: Segmented
Short DST - Started 06/01/2016 13:25:46
Short DST - Pass 06/01/2016 13:25:54
Long Generic - Started 06/01/2016 13:26:51
Long Generic - FAIL 06/01/2016 13:27:00
SeaTools Test Code: A995D7DE
SMART - Started 06/01/2016 13:27:42
SMART - Pass 06/01/2016 13:27:49
Short DST - Started 06/01/2016 13:30:12
Short DST - Pass 06/01/2016 13:30:20
Identify - Started 06/01/2016 13:30:41
Identify - Started 06/01/2016 13:30:54
Identify - Started 06/01/2016 13:31:13
Identify - Started 06/01/2016 13:31:46
Short Generic - Started 06/01/2016 13:32:47
Short Generic - FAIL 06/01/2016 13:32:56
SeaTools Test Code: A995D7CE
Long Generic - Started 06/01/2016 13:33:36
Long Generic - FAIL 06/01/2016 13:33:46
SeaTools Test Code: A995D7DE
Fix All Long - Started 06/01/2016 13:38:41
Fix All Long - FAIL 06/01/2016 13:39:06
SeaTools Test Code: A995D7CE
-----------------------------------------

You may download SeaTools for DOS from this website, SeaTools | Seagate burn it to a CD and run the tests. You can see the SeaTools for DOS guide also there.

hi ... have been away ... only got home a couple of days ago thus the delay in getting back to you ....
took your suggestion from your last posting but it turned out that the result was identical to the first time i ran the same test ... the screen and mouse locked and i wasn't able to continue.
have been giving a lot of thought to my problem and from the number of people i've spoken with, the general conclusion has been that the drive died due to a hardware rather than a software problem in that more than likely the heads failed.
basically, i've pretty much given up trying to flog a dead horse, write it off and invest in a good backup system.

i must thank you and all the others who have offered their suggestions over this problem. a great pity it didn't work out but it's time to stop.

again, thank you all.