Harry Potter (The night the Potter Parents Died)?

see using time turners is strictly under the supervision of ministry of magic. hermionee used it for completing her lessons and later for saving the hippogriff but as dumbledore told in the third book that the future can't be changed however u try. harry and hermionee had heard the sound of an axe in hagrid's pumpin yard and had thought that buckbeak had been killed but later on after timetravelling and saving buckbeak they found that it was the sound of the axe being hit on the ground out of anger by the man who was to kill buckbeak. what does that mean? it means that the future had been decided in the past itself. another instance is of harry seeing the prongs-patronus saving him and thinking it to be his father's ghost. later later he comes to know that it was his own future figure that had saved himself in the past. the future harry had saved the harry of the past from the dementors long before the future harry could probe into the past. what does that mean? it means that the future is already decided in the past and the future can't alter it rather the future lies the past itself and whatever is destined to happen will happen. no one can alter it.

harry's parents were destined to die and even the use of a timeturner couldn't save thier lives.

I don't remember his exact words, but Dumbledore warned about the dangers of playing with time. For example, for some reason it was very important that Harry and Hermione not be seen by anyone when they used the time-turner. Perhaps the complications of going back years would alter the time continuum too drastically for time to withstand the stresses of the change.

The amount of time that the time-turner was used for was only a matter of hours, not years. Herminone used it for class periods, and the night they saved Buckbeak was only a few hours as well.

However, this is, I think, the most important reason why it would not work:

You will note that they did not CHANGE anything by going back in time, they were just a second set of eyes seeing the scenes in the perspective of what had "already happened". For example, in the first passage of time, Harry was on the beach seeing the patronus conjured, and in the second set of time he was conjuring the patronus himself. The fact that he was there conuring the patronus did not change. Harry needed to be in both places at the same time in order for Sirius to be saved.

In this light, the fact that there was no one from the future saving James and Lily in the first passage of time means that no one could save them in a second passage of the same time.

If time-turning was readily available to just any wizard as a tool to actually change the past, just think of the havoc that would be wreaked by Voldemort and his death-eaters! I understand why it would be used sparingly and be seen as a very dangerous thing.

Basically the problem with your theory is that those things have already happened. So they cannot be altered. In Prisoner of Azkaban, the events were essentially happening concurrently, in this period of time and the other one. They didn't actually alter the outcome of events when they went back in time. Though they did have a role in how the events played out, the events turned out exactly the same. Buckbeak wasn't actually executed at first, they just though he was. Harry conjured the patonus but he did in the past also, he just didn't realize what he had done.

Why stop with saving the Potters? Why not go back to when Valdemort was born in the orphanage and foster him to a wizarding family?

The whole problem with what you suggest is it negates one or more books. Sometimes you have to accept that.

Here's a scene I'd like in the next book: Harry moves back into Grimwald Place and takes Dobie, Winkie, and Creature with him to mind the house. Can you imagine a very strong argument between Mrs. Black and Winkie?

I suspect Dobie is going to be an important ally in the next book.

Thats a good question. Maybe there is a reason as to why they can't go back in time for that. I still think the time turners are going to play a big part in book 7. Who knows, maybe a main character is going to die such as one of the 3, then they will use the time turner to save that character. I think that will happen yet in book 7

Well if that was done then I guess there would be no story because they would have been more prepared and able to find a way to beat Voldemort because isnt that basically what the books are about? Harry growing up and becoming a great wizard and beating him in a great battle?

if they did turn back time to tell the potters and longbottoms that voldemort was going to kill them who knows what could happen harry could not go to Hogwarts and never meet Hermoine or Ron... and that would be a terrible story I think.

obviously J.K Rowling hadn't thought up time turners until the 3rd book, otherwise that would be a legitimate question

Because

1.) It would take like 5000 turns....

2.) It would end the story and J.K. Rowling wouldn't have as much money.

It's just a story, not real life. Get a grip on reality.