Tuesday, January 27, 2009

Windows says my external USB hard drive is full when it is not - problem fixed.

I am posting this because I spent a couple of hours trying to fix a fault like this on Friday night. I was moving a file to my USB hard drive and windows reported that the device was full. I did a check and the drive was only quarter full. I checked the disk for errors and there were no problems. It had not gone read only, and there were no errors. It also did not need defragmented and the size was reporting correctly in My Computer and Tree Size (a very useful free utility).

After much faffing around I finally discovered that Windows was misreporting the fault. The drive was not full - the file was too large for the FAT 32 file system on the drive (it was a 4.2 GB disk image and the file size limit is 4 GB). All my machines are formatted NTFS which has no file size limit. I have not used FAT 32 for a long time so the USB drive must have been formatted that way out of the box without me noticing.

So the moral of the story is: don't take Microsoft's error messages at face value. A lot of time would have been saved if Windows had reported the error as "file too large for FAT 32 formatted disk".

5 comments:

  1. Thank you for solving this mystery: I just spent two days (not solidly, of course, but too many hours) trying to transfer a 4.2GB file from a laptop onto my desktop computer. I was able to transfer onto another laptop, but not onto the computer or any of its external hard drives (each with 400GB+free, or onto a brand new 16GB USB disk. Of course, my problem isn't fixed but at least I know Windows is lying.

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  2. I have the same problem too. One way to get around it was to open the .ISO file I was trying to transfer, and pull it over in sections. A real pain though.

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  3. Thank you -- it is nearly midnight and I'm working on a job due tomorrow - and your explanation saved me! I couldn't figure out why it said my drive was full !!! I had formatted it as FAT so I could use it on Mac and PC

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  4. http://www.technize.com/2008/07/14/how-to-format-usb-drive-with-ntfs-file-system/

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  5. Thanks - after spending 2 hours about to smash something I found this thread - I formatted the external drive as FAT32 b/c I had archive files going back 10+ years, and tried to put a pair of blu-ray movies on it with the above result...

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