If you were to go back in time for 8 minutes, what and where would you have gone back to and why?

I've recently watched the movie "Source Code" and although it was far from becoming an Inception 2.0 as some have suggested, it did leave some interesting questions regarding time traveling and the possibility of changing one's future over and over again.

Now here's how I understand it; there are spoilers though so you have been warned. I'll be actually summarizing the movie so don't read further if you want to watch the movie without prenotions at hand.

The protagonist, Captain Stevens played by the blue-eyed beauty Jake Gyllenhaal, has to locate a bomber by going back repeatedly, to a recorded past of a victim: the last 8 minutes of an already dead passenger, Sean Fentress, in a Chicago train bombing. Captain Stevens has succeeded in tracing and naming the bomber and in providing the necessary information to the authorities, the one who made the Source Code possible. He wished to go back to the "scene of the crime" though as he believes he'll be able to save the victims in the said train bombing. His reluctant contact from the Source Code team, Capt. Goodwin, gave him another chance to return to the said scene. Captain Stevens not only restrained the bomber and save the people on the Chicago train, he has apparently changed the future and now occupies the body of the Sean Fentress, who was one of the supposed to be dead passengers in the failed train bombing. Are you still with me?

What probably fascinates me about this movie is how vague and weird it was that Captain Stevens has changed the future when he didn't really time-traveled to the past. Source Code was comparable to a recorded program of events; it already happened, time is still moving fast-forward and you can't replace the future because you don't have access to the past. It was like Captain Stevens was repeatedly thrown in this recorded program so how come he was able to change the future?! 

Aside from that, the probability of time-travel is an eternal and never-ending interest for me. Imagine if you can undo everything, everytime! Wouldn't that be great?

Imagine going back in time again and again to figure out what went wrong in a transaction, in a campaign, in a project, your interaction with a prospect, the negotiation process and every bit of a significant event, be it of a work-related or personal one that is relevant to you. Just imagine the possibilities. Wouldn't that save businesses, millions, in test cases, in public scandals and humiliations and every bit of image-damaging action.

But just in case you're wondering if I'm a nut-case, I am thankful that is not possible. Well, as of now, that is. No work will get done if one always changes the course of the past, that would be tiring and we'd be wasting away our lives that way.

But the eternal question betrays my logical reasoning: If you were to go back in time for 8 minutes, what and where would you have gone back to and why?