It looks like a baud rate mismatch problem.
Look in the lower right corner of the Serial Monitor window: there's a number which tells you the baud rate it expects for the incoming data.
Now look at the sketch source code: there's a Serial.begin(xxx); call, where xxx is the baud rate Arduino uses to talk to the serial monitor (or whatever application is listening to the serial port on the PC). The xxx number in the sketch and the one in the serial monitor must match.
Hope this helps...