Rather than Symbol LED=0 try...

LED var PortC.0

Other common problems are...

1. You've not got a suitable Crystal or Resonator attached.
2. You've not defined a correct Oscillator setting (Config Fuses)
3. You've not handled MCLR pin properly by tying it to Vdd
4. You've forgotten to pay your electricity bill... (see also "I've got a flat Battery")
5. You've got the LED connected the wrong way around... (and might not have a suitable series resistor)