FIX: Restore security settings


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Article ID: Q700003

The information in this article applies to:

  • Direct I/O, version 4.0, 4.1, 4.2, 4.3, 4.4

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.


Any attempt to use or control the driver leads to an "Access denied" error. Even uninstallation is not possible.


There might be situations where the permissions to use Direct I/O have been damaged so that proper operation or uninstallation is affected. This article explains a way to restore default permissions .


To correct the problem follow the directions below:

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

  1. Logon with Administrator rights
  2. Back up the registry.
  3. Delete the subkey HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DirectIO\Security
  4. Restart the computer
  5. Start the Direct I/O Control Panel and select the Security tab.
  6. Select the Securable Item "Driver" and open the Permissions dialog.
  7. Review the settings:
    Administrators Full Control (All)
    BUILTIN\Account Unknown Full Control (All)
    Power Users Use (EIPGQSTUR)
    Users Use (EIPGQSTUR)
  8. Restart the computer.


Depending on the preceding user actions there may or may not remain problems using Direct I/O. If you still encounter difficulties in using Direct I/O you have to uninstall and reinstall Direct I/O.


This behaviour is by design.

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Last modified: 2018-04-24.
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