Built in LED won't turn off

From the moment i plugged in my Arduino into my computer the orange/yellow built-in LED won't stop blinking.
I can stop it with code but i want to know how to stop it by default and forever.
If anyone has a solution please post it here, I would appreciate it.

The only way to "stop it by default and forever" is to remove the LED from the Arduino board. Otherwise, just write your code so that it doesn't turn it on.

I do not quite understand the problem. Assuming an Arduino Uno / Mega etc

The led will blink a few times in quick succession when the bootloader starts.
Arduinos come preloaded with the blink sketch.

If you want to get rid of (1), rewrite the bootloader or erase the bootloader and upload via ICSP.
If you want to get rid of (2), you already gave the answer.

Thank you for replying guys/girls !