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I just purchased a 500 GB Toshiba Canvio 3.0 USB Drive (one of those usb-powered portable 2.5" drives). Initially, Windows reported its size as 465 GB, with about 458 free.

My primary hard drive is 420 GB w/ just < 400 GB used. I'm using Cobian Backup to copy everything from the primary drive over to the USB drive.

After copying about 260 GB of data, Cobian started reporting on every file that the disk was full.

I checked and sure enough, Windows is reporting "465 GB Used" and "0 bytes free"!

Yet when I view the drive's contents, selecting all the files/folders at the root level, Windows tallies up the contents at only about 260 GB!

There's nothing in the Recycle Bin, and I'm including all "hidden" and "system" folders in the total... so where did my other 200 GB of storage go?? Why the contradiction here??

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Check with WinDirStat to see where the space went. – David Schwartz May 23 '12 at 5:05
Do you backup everything "file-by-file" or "all-files-into-one backup archive"? – Robert May 27 '12 at 17:11
up vote 2 down vote accepted

Check the drive for errors (Drive Properties -> Tools -> Error-checking - > Check Now)

Or else (if possible)

Backup the data to some other drive & Format the problematic drive & move the data back to drive & check

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This is a great utility that will show you visually what the contents of your drive are. I use it all the time.

If you checked hidden and system folders it sounds like you might have a problem with the drive. Spacemonger will confirm the usage of the drive, and you'll use it in the future as well. (I have no affiliation with the devs)

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There are dozens of free apps that are not 6 years old that do the same thing, if not better. For example – Mxx May 23 '12 at 15:13

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