Today i made a mystake a terrible one,
In my arduino uno board i connected in the 5V line one wire with 12V.
I know that ATmega328P is getting hot, but if I replace it with one new ATmega328P with Arduino UNO bootloader, If i do that i could work?? I mean the arduino board with all the things normally.
Nearly everything on the board is briefly 12v tolerant on the 5v bus except the AVR chip. Replacing it is logical.
I'm going to bet it's not going to work, because the ATmega16U2 USB-to-serial interface chip was probably destroyed. It only tolerates 6V absolute maximum. See here for a longer explanation.
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The Rugged Audio Shield: Line In, Mic In, Headphone Out, microSD socket, potentiometer, play/record WAV files
Thanks for the advice , I will try to fix it my usb port was not conected when that happened. However I will try it's not very expensive to replace the micro.
And if it dont' work I will pay my fault =(
my usb port was not conected when that happened
That doesn't matter because the ATmega16U2 was still connected to the power supply.
Does the computer still recognise it as a serial port? If not this chip is fried.
Yes i plugged in, the board without the micro and usb doesn't recognize it. and also the small chip u told me is getting hot, So there is no chance to fix it ?? =(
Sorry no.
This is a surface mount device, unless you have a hot air rework station, and the skill to use it, there is no chance of getting the chip off or putting another back on.
Of course, if you did eventually get yourself a hot air station, QFN packaged components may actually be easier to solder/rework than TQFP (the ones with legs). I've done quite a few in work recently and was surprised how easy they are, compared to how hard I expected them to be.
Maybe see what you can pick up on the cheap, read some tutorials and have a play around? If your board is already broken you're hardly going to make things worse 
Grumpy_Mike:
This is a surface mount device, unless you have a hot air rework station, and the skill to use it, there is no chance of getting the chip off or putting another back on.
I got a hot air rework station a little while back, cheaply, but have been a bit frightened to tackle SMD stuff yet. I have visions of:
Apart from that, no worries! I should give it a go soon. 
I've done quite a few in work recently and was surprised how easy they are, compared to how hard I expected them to be.
Perhaps I should take inspiration from you BulletMagnet83.
but have been a bit frightened to tackle SMD stuff yet.
Try removing stuff first, and using a scrap board.
Blowing the parts away so they float along on a sea of solder
Yes that can happen but it is no problem because the solder does not stick to much being a thin film. Get a good pair of tweezers.
Everything not quite lined up properly
Yes that is the biggest problem.
Solder bridges
Use the minimum amount of solder, you also find out the value of a good solder mask.
I have done lot of experimentations like that.. I have few 328P that haing fault in few Digital pins due to mis-use the rest of the pins are working fine on them.don't worry, just load a sketch and see if it is loading...if yes you saved your Axx...Now, run a blink example on all the pins one by one and check with a led if it blinks..Note down the bad pins...
just load a sketch
But he said:-
Yes i plugged in, the board without the micro and usb doesn't recognize it.
And the USB chip is getting hot so you can't even program the board using the ICSP header...
Perhaps I should take inspiration from you BulletMagnet83.
Well, I'd NEVER done one before my supervisor gave me the task (it was removing and replacing some little QFN packaged mcu's)... I was bricking it a little bit, having pretty much the same visions of death and destruction. The ONLY thing that made it difficult was the lack of vacuum pickup thingies, and having to use regular tweezers instead. We have hot tweezers for the passives ^___^ I'm hardly God's Gift to rework, but if I can manage I'll bet others could too, even if they think they can't.
My advice would be to get some scrap boards and just practice removing and replacing things neatly without lifting tracks or breaking/cooking anything. Do your mistakes on stuff that was going to be recycled anyway! 