Data Execution Prevention

I recently had a nasty encounter with this feature which is designed to prevent viruses or malware from damaging your computer by preventing them from executing. In order for this to work you need a CPU and an OS that supports DEP.

My particular issue occurred while setting up a new PC. I found a good deal on an E-Machine at Wal-Mart ($300 for PC with 512 RAM and XP) which I thought would make a nice workstation at one of my wife’s offices where I just had a computer go down. Everything went great until I got to the printer setup. The setup actually went fine, but I could not print anything, DEP kept shutting down explorer. The printer was a 4 year old Canon printer / copier which had its own software along with the driver. No amount of adding program exceptions to DEP would make it work…this became very frustrating. After a little Googling, I found some info on how to disable this feature if you happen to have trouble like I did:

In Windows XP, check the boot.ini file. You will see a parameter on the OS line “/noexecute=” with a value following it, typically “OptIn” (the default setting). Change “OptIn” to “AlwaysOff” (no quotes) and restart. For a detailed description of DEP and Windows XP, see Microsoft KB article 875352.

In Windows Vista (which I am adding for the sake of completeness), things are a little different since there is no boot.ini file (like everything else in Vista, I don’t know why Microsoft couldn’t just leave well-enough alone). Here’s the basics:

  • Go to the command prompt.
  • Type bcdedit.exe/set {current} nx AlwaysOff and press Enter.
  • You should see a message saying that ‘The operation completed successfully.’
  • Restart the computer.

For more detailed instructions on this, see John Barnett’s Windows Vista Support DEP page.

In summary, DEP, like everything trying to protect you and your PC, is not perfect. Try your best to work with it, but don’t be afraid to shut it down if there are no alternatives to getting a program to function.

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