Arduino Nano 328 Heat if powered via VIN&GROUND

I cannot plug arduino from VIN and GROUND because the voltage regulator start heating like hell. I'v tryed to plug 3.7 and 7.4 volt, but it's the same, it will start heating more or less. For this problem i allready fryed a Nano board. Is that normal? Am i making some mistake?

The 5V Arduino Nano 3.0 requires at least +6V on the Vin pin. They recommend +7 to +12V.

Sounds like there was something wrong with your board or your wiring. If the output of the regulator is shorted (+5 connected to Ground) then the regulator will fry quickly.

Piton:
Is that normal? Am i making some mistake?

Do you have anything else connected to the Nano?