*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.
Step 3: Drums
Drum Machine is a Windows freeware application developed by Andrew Rudson that lets users play a virtual drumset on their computer using a drum controller from the Rock Band video games.
The program allows the user to set a different sound for each virtual drum, and a collection of default samples are included. Users can add additional samples in .WAV format and can also record their drum performances.
As of version 1.33 Beta, the program supports controllers from the Xbox 360, Nintendo Wii, Playstation 3 and Playstation 2 versions of Rock Band with dual drum set support. The in-game virtual drums can be heard by keyboard buttons representing different drum pads. This program is mostly incompatible with Windows Vista. - Wikipedia