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I have a 5TB hard drive (4.54TB in reality). Properties tells me I've used 4.45TB. It includes one system backup of roughly 1.8TB.

I decided to move everything (except system files, recycle bin, and that backup) to a new drive. Windows 7 tells me I'm moving 587GB. I've set all hidden and system files to be visible.

How is that one backup plus the rest of the files -- which together are about 2.5TB -- somehow amount to 4.45TB? What am I missing here?

marked as duplicate by Ramhound, Scott, Pimp Juice IT, bertieb, DrMoishe Pippik Dec 2 at 2:12

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  • Look up "alternate data streams" – K7AAY Dec 2 at 1:39

There are a few things you can try here.

First, you can analyze the fragmentation of your drive. It really shouldn't amount to that much space, but it's worth checking. You can do that with the built in defrag, or another tool like Defraggler.

Another thing to try is a disk usage analysis tool like Treesize to see what's taking up space (make sure to run as admin to find the hidden files).

A common culprit of high disk usage is the page file - you could try to reduce its size, or at least see how large it is currently by following these instructions.

Perhaps you'll find the cause using one of these avenues.

  • Pagefiles are normally tens of gigabytes. He's missing terabytes. – Loren Pechtel Nov 27 at 3:15
  • This doesn't seem to answer the question. – Blackwood Nov 27 at 3:16
  • Thanks! Treesize, which I opened as administrator, showed that a folder that showed as 0 bytes in both Properties and Windows Explorer, actually contained a backup and its updates. Now Ihave to figure out which update (the one I first saw or the one I'm now also seeing) is the more recent. I think I can figure out that one myself. – Andy Klein Nov 27 at 6:10

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