Suddenly can’t access USB hard disk in Windows 7: how to fix (reset permissions)

I fixed our neighbor’s laptop the other day, and I plugged my USB hard drive into it to transfer some files. After I plugged the drive back into my own computer, Windows 7 suddenly couldn’t access the disk (notice the drive space indicator disappeared in the first screenshot, below.

No amount of fiddling with the security/permissions/owner would bring it back, either.

This fix is to use the “icalcs” tool to reset the drive’s permissions. To do so, follow these steps:Launch the Command Prompt as an administrator (Start > Search for “cmd” > Right-click on “cmd.exe” and select “Run as Administrator”)

  1. Switch to your drive that is having problems (replace H: with your drive letter): CD /D H:
  2. Type: icacls * /T /Q /C /RESET
  3. Wait for a while. Mine took about 10-15 minutes.

When it’s done, you should be able to access the drive as normal.

Sources:

http://lallousx86.wordpress.com/2009/06/14/resetting-ntfs-files-security-and-permission-in-windows-7/

http://support.microsoft.com/kb/318754

Andrew Block

I (Andrew Block) am the Director of Analytics and Insights for MSP-C, an awesome brand journalism company in Minneapolis, MN. Insights are everywhere - and this blog explores that premise. One part geek and one part analyst, I like to blog about techy and insightful things. Or insightful techy things...or....

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  • inikiforIsaak Nikiforidis

    I had the same problem. In my case the solution was LockHunter (free).

  • Fred Shirley

    used the xp computer I have laying around and sure enough the external hard drive is fried…so that was the problem.

    now to find a new external hard drive…stink! actually is there any way to get the info off of it?

  • http://andrewblock.net Andrew Block

    Hmm. Do you have an XP computer you can plug it into? Maybe delete the drive and reformat using XP, and then see if 7 will recognize it. Unless of course you need to get the data off of it first?

  • Fred Shirley

    lol…yep it is!

    i have tried doing what you mentioned that is how i have gotten to this point. when i had XP on the computer no problems now that i have windows 7…problems with this external drive.

    when i do what you are asking it says I must initialize the drive and gives me 2 options to partition the disk both of which give me this result…incorrect function. got any ideas?

  • http://andrewblock.net Andrew Block

    Is this THE Fred Shirley? :)

    I’d try going to Disk Management (right-click on My Computer, go to Manage, then to Disk Management). Can you initialize the disk and assign a drive letter from that interface?

  • Fred Shirley

    what if there is no drive letter even assigned and it says

    Disk 1
    unknown
    Not Initialized

    above is what it says where the drive should be listed…just wondering if ya can help me out.