DiskWipe leaves you on your own recognizance for selecting drives, though it does present the removable media at the top of the list. But it will not stop you from overwriting your system drive, so... Don't do that. It's much like a loaded gun that relies on its owner to point it in a safe direction.

You could pay for more impressively-styled software, but there's no reason. The program worked for me, it most likely will for you as well. By the way, if you find it handy, Roadkil will accept donations at the Web site (though the donate button in the About dialog did not work for me).