Arduino UNO Pin problem!!

Hi! I have got an arduino uno. If I connect the 5v, GND pins to the breadboard and if i connect to it a led it work; but if I upload a sketch on arduino(for example blink pin 2) it doesn't work. If i connect a Ethernet Shield not even the breadboard work!!!! PLEASE HELP ME!

Ciao! Io possiedo un arduino uno. se collego 5v e GND alla breadboard e se collego un led esso funziona; ma se carico uno sketch (per esempio lampeggio pin 2) non funziona più. Se collego un EthernetShield neanche la breadboard funziona!!!!! PER FAVORE AIUTATEMI

Is your blink led work.?? Send your code and circuit setup here. So we can understand how you are trying to connect

if your board has a LED on it (usually pin13 also has a LED attached to it) then try using that one to see if your code is correct. Then if it works, it's probably something with your circuit. Remember the long leg of the LED goes to 5V and do not connect the led straight to the ground, but connect it to a small resistance (220 ? - 1 ?? should be alright) and THEN the resistance to the ground. Oh by the way, if you have connected the LED straight to the 5V and the ground, there's a big possibility that you have burnt it, so try with a resistance and a different LED. Hope i helped! :)