If I remember this right (it was a while ago), when I loaded my wrongly displaying drive into Paragon Partition Manager, it showed one partition which was the size being displayed in windows explorer.
The missing space, the large bit, was displayed as unallocated space. Using Paragon I was able to delete the small partition, and then repartition the entire drive taking in the unallocated space.
This fix was one of those trial and error things, and I should have made a note of what I tried, what failed, and what subsequently fixed things.
This is very interesting to me. I wonder if there were some resize option you may have tried in paragon, although I haven't used it much myself, perhaps a couple times here & there. I know in the utility I used for a Maxell drive, it basically flipped the partition.
In other words, it displayed a 1 MB partition but it also had a hidden 2 GB partition. The 2 GB partition was supposed to be the primary, but it was the hidden. The 1 MB was supposed to be hidden, but it was the primary. Since the 1 MB partition was the one being displayed, it wouldn't have worked to back up the data, since there was no data to be backed up on the 1 MB partition.
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The data was safe in the other partition, I just had to figure out a way to flip it back where the 2 GB (1.86 GB formatted) partition was the one being displayed when you plug the drive in, & the smaller 1 MB was the hidden.
I am thinking that this must be similar to the information on the drive that you are helping them with, although I am not 100% for sure, since I do not have the drive right here with me where I could check it out.
But I am definitely watching with interest, & it will be interesting to see if you happen on a solution to cause it to flip the partition with data on it to the primary one being displayed. As I recall correctly, a flash drive can only display a single partition on it, unless the drive's bit it flipped such that the drive appears as a HDD (Hard Disk Drive) instead of a FDD (Flash Disk Drive) to Windows.
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I might have to play with Paragon Partition Manager a bit to see if it can do it or not later. Ease US had no option to do so, although it would display the correct partition after the Maxell utility flipped the primary partition. I also noted that when the utility changed the status of the FDD to HDD, Windows would display both partitions (1 MB + 2 GB).
This was very cool, as I had never had a chance to see this happen prior to this, & to see it actually work was exciting to me. I hope that something I may have mentioned concerning flipping a partition, or some other piece, might trigger you to remember what it was you did when you had the allocated space problem.
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I am thinking, of course, that it must have something to do with flipping the partition on it, & that perhaps his drive is displaying the wrong partition. I could be wrong on this, of couse, but if you do remember what it was that you did concerning the allocated space, I shall make a mental note to try this on a junk flash drive I have, just for experiments...
The Maxell drive utility was specific to that brand drive & only worked with that drive, which is why I have such a high interest level in the outcome of this.