Poll :)

Go back and buy stocks of mIcrosoft, google or apple when they were just starting cause fuck you world, I'm now a multimillionaire! Maybe now I'll fund a cancer treatment research or something to even out the karma >.>

stop hitler maybe.but then if you alter the past you may never be born.

Go back 10 minutes ago and stop you from creating such a pointless poll.

Go back and stop myself from building it, therefore creating a time paradox that will DESTROY THE UNIVERSE!

I would probably go back to a time before one of my family members died. I'd spend more time with him, and do something to help delay his death, if possible.

I probably wouldn't time travel at all, and simply destroy the machine.
Why? Well... Who knows what could happen if I attempted to modify the past? It would surely affect the present/future greatly, but how and to what point? Perhaps nothing would change much, or perhaps the world would be completely transformed.

Also, are we talking about a time machine which literally makes the world go back in time, or simply takes you from the present, and brings you as you are (current age/state of mind/body) to the past? Also, if the case where your own self may travel back in time, then I would have to do everything possible to avoid being seen by my own self from that past, correct?

With that said... Also assuming that I, let's say, successfully stop 9/11. Then in the world where I originally come from, 9/11 hasn't happened in the first place since the "me" from the future stopped it. With that in mind, the fact that I would even think about stopping 9/11 to begin with wouldn't exist anymore, since the accident has never occurred yet... In that case, my purpose as a time traveling "me" wouldn't exist either, and so... In the end I finally don't travel back in time to stop 9/11, which means that the accident occurs. I think this is what we could call a paradox.

Another thing, when you travel back in time, you travel back to a point where the time traveling device has never been built in the first place. Doesn't that make it that you never end up traveling back in time?

...And that's why you shouldn't get me started on time traveling.
Just look at the damn wall of text... Sorry about that. I'm a time traveling junkie I guess. :P

Part of the arrogance of mankind is that we forget the depth of our ignorance and the shallowness of our understanding, all the while thinking we can do a better job of "running Life" than God can. We have only to look at how badly we run our own lives to see the fallacy of that kind of thinking.