Arduino not working

My arduino uno suddenly stopped working. The builtin led works, but if i hook an led or someting else up it doesnt work. Anyone knows how to fix this?

What did you do so it stopped working?
Unplug Arduino Plug it again.
Try to load empty program, then blink program, connect correct output and LED with correct resistor.

You could also burn your LED if you connected (for example a yellow one) without a resistor.