Is there such a thing an non hackable software or systems? It depends entirely on the amount of time and effort the hacker is willing to invest in finding a way in, and how long you let them try before sicking the dogs on them. Given enough time and resources, even the system in the basement in the safe is eventually hackable. It might need some serious hardware to do it.. but it can be done.
All you can ever do with systems in my opinion is make it harder, slower and with more chance of you finding out that your being hacked so you can do something to stop it.
The default installs these days are pretty good, and as already stated, stopping anything running that you don't need and performing the usual common sense tasks with passwords and user permissions etc will make it harder.. but never assume your safe (especially on a windows box, as a windows admin I'm amazed you would ever assume that you are safe).