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My company bought a bunch of flash drives, 500 1 GB drives, to be loaded with marketing materials and given out at a trade show. While testing the loading of the drives I noticed that some of them have used disk space, around 25 MB. I have checked for hidden files and run scans, but nothing comes up. Is this just bad formatting of cheap drives or is there a security risk? After reformatting one, it showed 948 MB free space, which is what the majority of the drives are showing. About one out of six drives have some used space.

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One out of six drives have a different amount of free space than the others? – user142485 Jul 12 '12 at 15:47
I haven't looked at them all yet, but so far that's what it looks like. – JTB Jul 12 '12 at 15:54
I agree with the answer below but depending on the space difference it shouldn't be different on 1/6 of them. – user142485 Jul 12 '12 at 15:57
Try to reformat a sample from both kinds of drives and see what you get. A slight chance is that the drives have different hardware. But they are more likely to just have different formatting on them. I'd (quick) format all of them anyway before distribution. – jpe Jul 12 '12 at 16:01
If I reformat to NTFS, they have 949 MB capacity, 916 MB free space, and 16 MB used space with no files showing. If I reformat to FAT, then they show 948 MB capacity and 948 MB free space. I'm probably just being paranoid here, but I'd rather be safe than sorry. – JTB Jul 12 '12 at 16:12

All file systems have overheads. These are usually displayed as used space. In your case it's formatted with NTFS which have significant overhead. It will get better if you format them as FAT or FAT32.

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They are formatted FAT. I was thinking the file system overhead was the 52 MB that was not showing up as free space or used space. They are 1 GB drives, with most showing 948 MB free space and no used space. The ones in question are showing 24.6 or so used space and 923 MB free space. – JTB Jul 12 '12 at 15:57
@JTB - I don't understand what the problem is. How much space do you expect to be able to be used exactly? – Ramhound Jul 12 '12 at 17:11
I expect there to be zero used space on a new drive. The problem is that some of the drives have used space, and I can't find any files on them. – JTB Jul 12 '12 at 17:35
@JTB - What tool are you using to format them? Post a screenshot of the disk mangement tool within Windows indicating what you mean exactly. Unless the properties for the drive say there are files, then nothing is taking that space, that is simply the space aviable. You do understand flash memory can wear out and no two devices will have exactly the same amount of storage right? – Ramhound Jul 12 '12 at 19:48
Also might want to consider exFAT format, aka FAT64, which overcomes some of FAT32's limitations without all the overhead of NTFS. – martineau Jul 13 '12 at 0:31

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