*Please comment if you know of any programs that I may have missed.
Step 1: Microphone
Step 2: Guitar
Download [http://dodownload.filefront.com/12087935//55f559c3584a5236428fd640ba9a8394194766fd4a2c83da3704f751b1f04324d1f63691e94690fc here].
In this package, you get JoyToKey and Electronic Piano. Electronic Piano is just a keyboard sound maker. Instruments on your keyboard (like GarageBand's Keyboard synth). Now, what JoyToKey does is it takes joystick buttons (Rock Band guitar fret buttons) and turns them into keyboard shortcuts. For example, the green fret becomes the letter Q. When you go to Wordpad and hold the green fret, you see Qs. So open up Electronic Piano and JoyToKey simultaneously and you'll get a Rock Band guitar synth. I've included a file that's already configured the Rock Band guitar for JoyToKey, but if it doesn't work, you'll have to configure the buttons yourselves.