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Weird disk usage discrepancy

Last response: in Storage
December 29, 2010 11:45:48 AM

I have a brand new WD Caviar Black 1 TB drive, which has 931.5 GB of usable space. I use it for storage (nothing related to the OS, which is Win 7 Pro).

I have three folders of data on the drive, totaling 429.GB. By my calculations this should leave me with about 502 GB of free space.

Today I noticed that Windows Explorer (aka "My Computer") is showing 432 GB of free space and disk management is showing 433.86. They both show the total usable space as 931.50 GB.

Any idea why there would be a 70 GB discrepancy from what my math says I should have available? I don't quibble over minor reporting differences, but this seems weird.

I have Win7 set to show hidden files, if that's relevant.

Any advice would be appreciated.

December 29, 2010 11:56:07 AM

Update: 5 minutes after posting this I rebooted and the total free space dropped to 428.6 GB, without making any changes. ????
January 4, 2011 11:12:25 PM

It turned out that this was due to system restore being turned on for that drive. These files don't show up in windows. As soon as I turned it off for that drive and deleted the restore points, I got the real estate back. I wasn't really concerned about the space; I was just concerned about the possible cause.