Initialize disk warning after setup Security in Property

Your drive is corrupted. Your actions should not have caused a reboot of the Operating system.
You can try recovery tools i.e. getdataback or R-Studio if the data is irreplaceable or very important time to send it to a disk recovery provider

As David noted, the drive is effectively reflected as bad.
if it is gone, it means the SATA data exchange .....is not there.  
Possible data recovery as the sole remedy.

i would try to make an image of the drive -  if that is possible, you may make a copy of your drive to work on
use any imaging software
but if the drive does not show up - you may need the recovery service as suggested

***i hope you have a backup ?  if not - this shows you it is high time to install backup rules

I bought Spinrite but it did not work, They said it is a file system issue not data recovery issue.

i use HDDRegenerator instead - but AFTER running a short disk diag - to Ensure the disk works ok
what brand/model is it  ?

Seems like you accidentally removed the partition table. or more likely stuck an empty gpt partition table ontop an existing mbr table.

Gparted provides a bootable usb key that can recover partition tables through an "analyze" command.

I got the impression that the asker did not accept the initialize prompt.

My question is when I click on the Initialize Disk, will my existing data on that drive be deleted?

Yes!

Hmm... i would say no.

Initialize will merely partition the drive. Partitionning will make the data most likely unavailable as it will create an empty partition table. Nevertheless the data is still there unless you format. And even a quick format does not destroy the data.

You are most likely in an accidental re-partition scenario, which is actually easy to recover from

"which is actually easy to recover from" . How do I do it?

See my previous post. Gparted should detect superblocks and or filesystem boundaries

I did not do anything today but I came home and turned on my desktop and my hardrive is back. It said Healthy under Disk Management. However, when I clicked on it, it said Access Denied. How do I remove the security?

You should come the drive to a new one as soon as possible
Addressing the accessibility is best after the data is on the new drive.

Arnold, I do not understand your comment. Sorry.

Clone the drive.
The manufacturer of your drive li likely provides tools to clone the drive to another.
Is the 1.5TB drive a green western digital ?

yes green western

Best get a new 1.5 blue and clone the data to the new drive.

Wdc.com download and install acronyms wd tool through whose use you can clone thedrive.
You can get a Seagate and get the disc wizard. From their support site. It does cloning of secondary drive without a need to reboot..
.

it said "the cloning process will delete all content from it". Note that this drive is not my main drive. It is used for storage only.

https://www.diskpart.com/articles/western-digital-data-migration-7201.html

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appreciate the recommendations. I will need to get a new hardrive and will clone it.

you may want to post the smart data of that drive. from what i gather, there is no guarantee it is actually dead. clonig will only work if the drive works.

i never got an answer on my Q : what brand/model is it  ?

1.5TB wd green

you can use the WD lifeguard then : https://download.cnet.com/Data-Lifeguard-Diagnostic-for-Windows/3000-2086_4-10972008.html

the WD greens had their issues. fewer tinkering IMHO, get the data cloned. the work on regaining access using the new drive while the current can be in the "background if needed"

test the drive first - if the drive does  not work properly, you can't clone it either

While I do not disagree. Testing like cloning adds load/use of drive. Cloning software potentially get some of the data in time. Testing that leads to a total failure..
Much depends on how much the data is worth to you if you do not have a backup of data. Depending on the damage, it can commonly cost from 200 to 2500.

arnold - i suggested a SHORT test - to test the basic functions

if the drive still works fine and a SOFTWARE problem caused the initial message and wiping of the partition table which is likely, cloning will not help, both cloning and testing will simply reduce the disk's lifetime, and every random action is an extra risk.

the very first thing to do, is a diagnosis : boot on a live cd and check whether the drive is recognized properly. fdisk and gdisk allow to view the partition tables. gparted can do the same and additionally restore them. chances are the disk will simply work without extra actions. chances are gparted will solve the mess that was created by windows while "taking ownership" of the drive.

anyway, if the disk is actually dead, neither the test not the cloning will ever succeed.

he told us the drive is seen in disk management - so no need to boot from live cd imo
and i still thingk you should do a short test - if you want to know if the disk operates ok

Disk Management saw the drive as Unallocated. But now (and I don't know how), it can see it as healthy. When I clicked on it to explore. it said Access Denied. i found Minitool Power data Recovery. I installed and am currently running a scan with the software. I can see all my folders and files through that software. but it is still running.

whichever method you use, either a recovery software as the one you mention or a disk cloning tool, you need a new drive onto which to write the information either from recovery or through data cloning.

What I've seen in similar is that after a while of working, the drive "heats up" and became as you had before, unallocated/inaccessible.

access denied would seem to be a permission issue.

what does the security tab of the drive's property show ? in advanced, you should have something like "users" or "authenticated user" with rw privileges

IMHO, if a drive at one point or another showed UNALLOCATED, the fewer things one does to the data on the drive including taking ownership, running software that scans the drive, testing the drive, etc. is time best spent on getting the data off.
IMHO, the least amount taken is to clone it. A recovery software is a two pass, first look through what can be seen, then go through and actually copy the data.
A clone is a one pass, while scanning through it replicates to the new..
Yes as nobus pointed out, if there are media issues, the cloning software could hang up at trying to access a "bad block" before continuing...
My thought is either take the cost hit on an additional drive. or if the drive fails completely, you are looking at the consideration on whether to do a data recovery that can be from $200 to $2500 depending on which data recovery vendor you choose.

Unallocated simply means the partition table was trashed. Rebuilding it may or may not work but won t trash the data.

If the drive is actually dying, copying the files puts much less strain on the disk than clonig it, and the filesystem can recover from many errors the cloning software will bump on.

Hmm, I understand; though, would it depends on the cloning software or not?
I.e. My experience with acronis (wd) or seagate' discwizard option, they clone/copy usable space.
The Linux based dd which does a block by block, sector by sector copy could understand the concern/impact.

To clone or copy, one needs the additional drive onto which the data should be copied.

Loss of partition table is an indication of ...either circuit board issue or corruption of the relevant Sectors?

How do I copy the file if I have a Access Denied? The Security said Full Control for all users.

@arnold : i am unsure what acronis does, but assuming it is filesystem agnostic, it cannot handle redundant copies of filestystem structures like an actual filesystem. At best it can guess which sectors are actually used and ignore unused ones. Sas drives with vendor provided software should do that efficiently since they maintain a map of used sectors in the controller. I am unsure this is feasible with other drive types.

@leblanc : if you boot a live cd, the windows permission issues won t arise. And if you use windows, it will most likely be simpler to solve the actual issue than bother with cloning. And it is fairly possible the cloned drive will produce the same errors.

... but if you do clone, i am interested in the results

@skullnobrains. Good idea. So I need a live CD. How do I make a live CD?

Your system is ntfs as to liveCD, download Ubuntu, centos, Debian, knoppix, and burn it
ISO can be burned using win7 and newer..
Then boot from the media.

here the Ubuntu cd  :  https://ubuntu.com/download/desktop
it is an iso file, so you need an iso burning tool to burn it to a cd
i use the xpcdburner for that - very easy to use : https://cdburnerxp.se/nl/
when you start it - just select " burn iso image"   and point it to your iso file

That did the trick. I can read all my files with Ubuntu. I will backup all the files to another hardrive and will reformat the old one. Thx

If you have enough space, you can backup to the Sane partition and simply destroy and recreate the problematic one. Good to see the data did not get trashed.

I think something with the files security in Windows that is messed up. No idea how to fix that.

sorry, my previous comment is not helful. Mixed threads. If you do haved a drive around, you re all set.

 actually, i m not  even sure the drive will be usable in that same windows install after repartitionning unless you toy with removable drives.

You can also try to uninstall the drive in the device manager and let windows redetect it upon next boot.

I think I will just move the files to another drive and reformat the old drive. Appreciate you all for providing advice.

here some tools to handle that :  https://www.netadmintools.com/ntfs-permission-auditing-reporting-software