This is my attempt at the obligatory time travel story that all Harry Potter fanfic writers have to attempt at some point.
Harry goes back in time to the start of his first year, and so quotes have been taken from Harry Potter and the Philosopher's stone (put in italics). I'm planning on writing out most if not all of Harry's second try through Hogwarts, so this will probably be a long fic or a series of fics, but the changes to the plot in the first book or two will be minimal, however I don't want to just rewrite the books on this site - we've all read them. Not a lot will change to plot of Philosopher's Stone, but as time passes bigger changes will happen that alter the plot, but there needs to be a base start.
As usual, if you don't like this story, don't read it! I won't be offended, and you don't need to waste your time reading something you don't enjoy! That said, I hope you like this!

"I've got a choice?"

"Oh yes." Dumbledore smiled at him. "You have options. We are in King's Cross, you say? You could go back, or you could be able to… let's say… board a train."

"And where would it take me?"

"On," said Dumbledore simply.

Silence again.

Harry looked around, thinking about the first time he had been to this station; 11 years old and on his way to a magic school for wizards. He could see this dream-scape limbo's version of the wall that would lead to platform 9 3/4.

"Voldemort's got the Elder Wand." He said.

"True. Voldemort has the Elder Wand."

"But you want me to go back?"

"I think," said Dumbledore, "that if you choose to return, there is a chance that he may be finished for good. I cannot promise it. But I know this, Harry, that you have less to fear from returning here than he does."

Harry glanced away from the barrier between platforms 9 and 10 at the raw-looking thing that trembled and choked in the shadow beneath the distant chair.

"Do not pity the dead, Harry. Pity the living, and above all, those who live without love. By returning, you may ensure that fewer souls are maimed, fewer families are torn apart. If that seems to you a worthy goal, then we say good-bye for the present."

Harry nodded. "Yeah. Too many people have been hurt, and killed."

"And you could prevent more."

Almost before he realised what was happening, Harry's feet were moving, carrying him away from Dumbledore, away from the small, moaning creature under the seat and the war and suffering it represented.

"Harry?"

But Harry didn't stop. A small smile was spreading across his face as he thought of the possibilities, of all the things he could do, the things he could change. His footsteps sped up as he drew nearer, until he was practically running.

As he reached the barrier, he closed his eyes.

He collided with a wall of noise, almost knocking him backwards as his eyes snapped open. Harry stumbled, momentarily blinded by confusion until he felt the hard metal of a trolley handle under his hands, and the mad swirl of colour and noise settled into the chaos of platform 9 3/4.

"Oh my god." He whispered, staring around.

The scarlet steam engine was waiting next to a platform packed with people milling around underneath a sign reading 'Hogwarts Express, 11 o'clock'. Harry looked behind him and saw the wrought-iron archway with the words Platform Nine and Three Quarters on it.

He had done it.

Smoke from the engine drifted over the heads of the chattering crowd, while cats of every colour wound here and there between their legs. Owls hooted to each other in a disgruntled sort of way over the babble and the scraping of heavy trunks. Harry looked over the large trolley he was pushing and felt tears spring into his eyes as Hedwig stared back at him from inside her cage.

The overwhelming sounds were drowned out as Harry stared into her bright amber alive eyes, pushing his trunk towards the train. With a start, he looked around the station, his breath catching with every person his eyes fell upon who would be dead within the next seven years. They all looked so small and young. Crabbe, Justin, Roger Davies, the woman dropping off Hannah Abbott, Cedric-

No.

He wouldn't let it happen again. He would change things. He had been given another chance; somehow managed to go back in time through some sort of imagined 'afterlife' in his head. He wouldn't let the world go through the horrors he had been through once already; he knew they were coming. Oh god they all looked so young.

Harry heaved his trunk onto the train, struggling with the awkward weight. He was short and weedy and eleven again, and the actual reality of what he had done and what was to come began to sink in.

His heart leapt into his throat as his vision seemed to go double, and two identical (young) redheads helped him stow his trunk in the corner of the empty compartment. The Weasley twins were so much younger than the last time he had seen them together, so much more whole.

"Thanks." Harry managed, pushing his hair out of his eyes.

Fred's eyes widened. "What's that?" He asked, pointing at Harry's forehead.

"Blimey." Said George. "Are you…"

"He is." Fred breathed. "Aren't you?"

"What?"

"Harry Potter."

"Oh. Yeah."

The twins gawped at him, and Harry felt a pang of betrayed annoyance. The Weasleys had been a few people he could count on not to stare. He shook his head. That was unfair. He'd only just met them.

To his relief, Mrs. Weasley's voice called over the noise of the platform, diverting Fred and George's attention, and they hurried off to their mother. Harry dropped onto the seat, the adrenaline brought on by seeing Dumbledore and Fred and platform 9 3/4 and dying beginning to wear off, leaving him feeling numb and raw and drained and excited.

He had travelled back in time.

Or at least to some sort of alternate reality where he was 11 and had his memories and everything was happening the same way once again. When he had run through the barrier in his head, he had only had the vague idea that it might work, and looking back on it now seemed reckless and dangerous and unlikely to have worked, but at the time it had seemed like the best and only way to make things better, the way dreams only really make sense whilst you're in them. Less than an hour ago, Harry had been fighting death eaters and facing down Voldemort, and now he was sat on a train in his 11 year old body, about to start hist first year at Hogwarts, again.

A whistle sounded, and his eyes snapped up, wand in hand as he looked around. He immediately felt foolish for doing so as the final noises of people climbing on board and saying goodbye to family sounded up and down the train. Embarrassed, Harry quickly stowed his wand back in his pocket, missing the holster that had been strapped to his arm for over a year. There was no danger. These people weren't at war.

But they would be if he couldn't change things. The task he had set himself suddenly seemed that much more impossible.

The train started moving with a jolt, and Harry peered out the window, watching Mrs. Weasley wave off her sons, Ginny chasing after the scarlet steam engine as it picked up speed. They rounded a corner and buildings flashed past the window. Excitement battled with fear and nerves in Harry's stomach, and he jumped again as the compartment door opened, barely stopping himself from pulling his wand on Ron.

"Anyone sitting there?" He asked, pointing at an empty seat.

Harry shook his head mutely, and Ron dropped down opposite him. He glanced at Harry then looked away quickly, staring out the window, his eyes occasionally flicking back to Harry's face. Harry himself wasn't nearly as subtle. His eyes were fixed on Ron, taking in how young he looked, the lack of scars, the dark smudge on his nose.

"Hey Ron."

The twins were back.

"Listen, we're going down the middle of the train – Lee Jordan's got a giant tarantula."

"Right."

"Harry." Fred said. "Did we introduce ourselves? Fred and George Weasley. And this is Ron, our brother. We'll see you later." The twins slid the compartment door shut behind them.

There was a moment's quiet.

"Are you really Harry Potter?"

Harry nodded.

"Oh. Well, I thought it might be one of Fred and George's jokes." said Ron. "And have you really got… you know…" He pointed at Harry's forehead.

Harry pulled back his fringe to show the lightning scar.

Ron stared. "So that's where You-Know-Who…"

"Yes."

Something in his tone clearly dissuaded Ron from asking any more questions.

Harry remembered the first time he had taken the Hogwarts' Express with Ron. He had been so excited, so curious, so full of questions for Ron about magic and his family. But this was Ron. His best friend. Harry didn't think there was much he didn't know about him. How could he ask questions about what Bill did for a living when he had been to the man's wedding? But how else could he explain knowing those things without having first asked questions?

Somehow, he got through the train ride, and if Ron noticed that somehow he knew which Bertie Botts to avoid despite 'never having eaten them before' he hid it well. Harry had clenched his hands so tightly his nails had cut into his palms when Ron pulled out Scabbers, and it brought about a chain of questions and thoughts and possibilities that spiralled around his head. He gave himself some time to pull himself together and think things through by suggesting to Ron that they change into their robes as the light outside began to fade.

How much could he change? There was so much suffering he knew was coming; Ginny, Riddle's Diary, the basilisk, Dobby, Sirius, the Triwizard tournament… but if he changed things straight away the future would be different, and he would have no way of avoiding Voldemort's reign of terror. But was he really going to let Sirius rot in Azkaban whilst Pettigrew gorged on chocolate frogs? He felt like Dumbledore, manipulating things just the way he wanted them.

He was brought out of his thoughts by the compartment door sliding open once more. Malfoy stepped inside, flanked by Crabbe and Goyle.

"Is it true?" He said imperiously. "They're saying up and down the train that Harry Potter's here. So that's you, is it?"

"It is." Harry replied.

"I didn't introduce myself last time we met." Malfoy said. "My name's Malfoy. Draco Malfoy."

It took Harry a moment to remember that he had run in to Malfoy in Diagon Alley before meeting him once again on the train.

Malfoy managed to look down his nose at Ron, an impressive feat given he was at least 3 inches shorter. "I see you're associating yourself with Weasleys. I'll give you some advice, Potter. You'll find some wizarding families are much better than others. You don't want to go making friends with the wrong sort."

"The wrong sort?"

"Everybody knows the Weasleys have more children than they can afford. You hang out with riffraff like them and that Hagrid oaf it'll rub off on you."

Harry frowned, pretending to think it over. "So instead, I should hang out with people like you? Who insult people they've never met to their faces and disrespect Hogwarts faculty?"

"I-"

"Get out." Harry said calmly. "I don't like bullies. Don't become one, Draco."

Malfoy's cheeks tinged pink and he turned on his heel, storming out of the compartment.