I'm not responsible for anything that happens to your computer because you followed this guide. This method is not guaranteed to work.

Open the start menu, type in 'cmd' and run CMD as administrator.
Now type in "bcdedit.exe /set {current} nx AlwaysOff" and press enter.
Restart your computer and D.E.P. should be disabled now.

If you want to enable D.E.P. again, repeat these steps but fill in "bcdedit.exe /set {current} nx AlwaysOn" instead.