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Wednesday, July 8, 2009

Disable Data Execution Prevention (DEP) in Windows Vista or in XP

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Viruses and other security threats can control your PC by executing code from within memory. To prevent damage, the Data Execution Prevention (DEP) feature in Windows operating system monitors program applications to ensure they use protected memory in a safe manner. Any incorrect usage, by an application, of protected memory and Data Execution Prevention steps in and automatically closes the application.Simply,Data Execution Prevention (DEP) is a set of hardware and software technologies that perform additional checks on memory to help prevent malicious code from running on a system. In Microsoft Windows Vista, Microsoft Windows XP Service Pack 2 and Microsoft Windows XP Tablet PC Edition 2005, DEP is enforced by hardware and by software.


The primary benefit of DEP is to help prevent code execution from data pages. Typically, code is not executed from the default heap and the stack. Hardware-enforced DEP detects code that is running from these locations and raises an exception when execution occurs. Software-enforced DEP can help prevent malicious code from taking advantage of exception-handling mechanisms in Windows.


There may come a time when have to disable DEP either for the purpose of troubleshooting a problem or otherwise.The instructions to disable Data Execution Prevention (DEP) in Windows Vista or in Windows XP is given below:


Disable Data Execution Prevention (DEP) in Windows Vista



  • Click the Windows Vista Start orb.

  • In the Start Menu, navigate to All Programs, then Accessories.

  • In the Accessories menu, right click on “Command Prompt” and select “Run as administrator.

  • You may need to provide Administrator credentials at this point.

  • In the Command Prompt window, type “bcdedit.exe /set {current} nx AlwaysOff” and press Enter.

  • You should see “The operation completed successfully.

  • Close the Command Prompt.

  • You must then reboot your computer. Failure to do so will cause weird problems later on.


If you still run into problems, you can run setup from the command line like so: setup.exe /ignoredeperror



Note: if you ever need to enable DEP again, you can follow the same steps except provide “AlwaysOn” as the final parameter to the bcdedit.exe command in the Command Prompt.ie,bcdedit.exe /set {current} nx AlwaysOn


Disable Data Execution Prevention (DEP) in Windows XP



  • Right click on My Computer and Select Properties.

  • Click the Advanced tab, and in the Startup and Recovery section, click the Settings button.

  • In the System Startup section, click the Edit button.

  • Now find the text that says /noexecute=OptIn.

  • You need to replace OptIn (which the default) with AlwaysOff.


Be sure to enter this text carefully and exactly as it’s mentioned above. Failure to do so could prevent your computer from booting.

Your boot.ini file should read:/noexecute=AlwaysOff



  • Click File and then click Save.

  • Click OK to close Startup and Recovery window.

  • Click OK to close System Properties windows

  • Restart your computer.


This setting does not provide any DEP coverage for any part of the system, regardless of hardware DEP support.


Verifying DEP is Disabled in Windows XP



  • Right click on My Computer and select Properties.

  • Click the Advanced tab.

  • In the Performance section, click the Settings button and then click Data Execution Prevention tab.

  • None of the DEP settings should be available.Click OK to close Performance Settings window.

  • Click OK to close System Properties window.


DEP is now completely disabled in Windows XP. If you want to enable it again, follow this guide but instead of replacing OptIn with AlwaysOff, replace AlwaysOff with OptIn (the default).


Also you can try….


If a program is failing and you want to disable DEP to see if that is the cause. Here are the steps. (Just disable DEP for the program in question and don’t disable it for your whole system.)




  • Click Windows Vista/XP Start

  • Select Control Panel

  • Select System

  • Click the Advanced tab

  • In the Performance region select Settings

  • Click the Data Execute tab in the dialog box that opens

  • Select Turn on DEP for all programs and services except for those I select

  • Click Add.

  • The open dialog box will open. Browse and select your application.

  • Click Open

  • Click Apply

  • Click Ok

  • Reboot


IMPORTANT: After making any changes in the boot.ini file, you must restart your computer.




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