Download Virtual Piano, to play the piano on your PC keyboard
Virtual Piano allows you to play your synth by making the computer keyboard into a 4-octave piano keyboard.
You must have a MIDI output device, as well as a sound source to use this program (anything from a Soundblaster to a Midi TimePiece will do), then just run the program, configure the MIDI devices, and start jamming!
Normally you won’t need to make any changes to the configuration. When the application starts, your keyboard will play music. When you close Virtual Piano, your keyboard becomes again a typewriter.
Unfortunately the program does not give a map of the musical values for each keyboard key. There is some documentation, that explains roughly what everything means.