Summary:

Going back, changing everything...
Not so simple, considering no one seems willing to cooperate. But, hey, at least Harry isn't alone in this madness, and truth be told, he's having perhaps a little too much fun upsetting everyone around him. In his defense, returning from the dead always has a certain effect. Going back in time shortly before his fifth year... could be even worse.
Or better.
A matter of perspective.

In other words: Harry goes back in time to the summer before his fifth year at Hogwarts with the intention of changing as much as possible. The good news is that he doesn't have to do it alone. The bad news is that it might complicate things a bit.