wav files are encoded by 'drawing' out the sound waves in 2d using bits (1s and 0s), including other information such as volume, wavelength, wave frequency, wave amplitude etc.
A wave player is needed to convert these digital signals into meaningful sound units.
Notepad just converts digital signals into characters. So basically its like a translator trying to translate a foreign language. If you've used an online translator you would know that what you get sometimes are sentences that don't make sense.
This method of 'conversion' from wav to notepad is not reversible, because important digital information is lost when in notepad form because it is unable to translate many signals.
Use a wave editor (Nero wav editor, iTunes), to see what a .wav file 'looks' like and how to edit it. If you are a good programmer, you can use an editor and find out how a wav editor makes sense of audio digital signals