How can I “reset” an Arduino board?

Question

I\'ve uploaded a sketch to an Arduino Uno whose loop is something like this:

void loop(){
    Serial.println(\"Hello, World!\");
}

So, now,

Answer 1

If nothing helped then you should arrange one more board and try to flash it through the Arduino as ISP option as shown in Arduino as ISP and Arduino Bootloaders or From Arduino to a Microcontroller on a Breadboard.

Instead of a boot loader, you can select your own programs to flash via ISP.