Locate a spare desktop keyboard you no longer use.
Download a software program like Piano FX, KB Piano or ARPTON Synthesizer (see Resources). Follow the on-screen installation instructions.
Connect the external keyboard to the USB or PS2 port on your computer. If you are using a desktop computer, disconnect your regular keyboard and connect the one you will use as a piano keyboard.
Open the piano program. Press each keyboard key to identify the note generated by the piano program. Write the note each key plays on an adhesive label. Cut the keynote from the label to the size of the keyboard key. Make your cut keynote slightly smaller than the keyboard key, so that the adhesive label doesn't interfere with other keys. Stick the marked keynote label over the key. Repeat the procedure with all the other keys on the keyboard.
Play your newly made piano keyboard on the computer.