You'll see two options in that window click the second option that says "Turn on DEP for all programs and services except those I select."
8. when you are finished with that then click the 'add...' button it should be visable at the bottom of the box. then you have to find where the file 'explorer.exe' resides on your computer most of the time it's something like this c:\windows\explorer.exe anyway add explorer to that list.
It'll give you a warning just ignore it and click ok. Then you reboot and if you try it everything should work just fine.
Try this. If it fails, please reset to original.