Gigaware controller on vista
You don't (and can't) disable DEP for the controller (a gamepad controller isn't an application, it's a device which uses a driver, Data Execution Protection applies to applications ie .exe files), it's the game or emulator you disable DEP for, so that you the game can run, completely free of security bindings, and then you would be able to go into the game configuration menu and select your gamepad, and calibrate it. Calibrating means the game detects you gamepad and applies the specific functions to each button.
One way to be sure is to disable DEP for everything, then install a game, and THEN plug in your gamepad. Then start the game/emulator and go to the configuration menu within the game/emulator and set up the gamepad calibration in there.
If it doesn't work, then you haven't installed the drivers for the gamepad properly, or haven't installed the correct driver.
Before doing any of that, you would have checked in Control Panel and Gamepad Controllers, double clicked the Gamepad in the list and pressed Calibrate, to enable generic gamepad functionality.
If you hadn't done that, do so now.
If it still doesn't work, then NOW disable the DEP (either all DEP or for the game/emulator you want to play). Unplug the Gamepad and load up a game. Then plug the game pad in. Set up the gamepad from within the game/emulator config menu, which differs from game to game, of course, but is more or less the same.
If it doesn't work.. re-install the correct driver for the gamepad.
Also make sure your operating system is fully updated and you're plugging the gamepad into a usb2.0 port. and have rebooted after installing the gamepad usb driver.
That's everything you need to know..