How do I know if a PIC is dead ?

[falingtrea]

If you did something to the Vref pin, you only may have messed up the analog circuitry. I would do an LED check of the specific pin you overvoltaged. Also was the voltage directly on the pin or through a series resistor? The resistor would have probably protected the pin.

[Ingvar]

Overvoltage with no current limiter is more or less a bulletproof way to fry a pin on a pic. I've never seen the entire pic beeing fried from it though.