To disable DEP, you have to make a change to the BOOT.INI file in the root.
Boot Windows into safe mode.
To boot into safe mode, press F8 a few times after the BIOS has finished its posting.
Once you're in safe mode, use these steps:
Right-click on My Computer and select Properties.
Click on the Advanced tab.
Click on the third buttonâ€”settings for system start options.
Click on the Edit button to edit the boot.ini file.
Carefully edit the /NoExecute=OptIn string and change it to AlwaysOff.
This part at the end of the line should now read: /NoExecute=AlwaysOff
Save and close the dialog boxes by clicking on OK.
Now reboot in normal mode again.