GuitarPadDigitalTuner  1.01  is a program that enables you to automatically
tune  your  guitar  using  your  computer  microphone.  If no microphone is
available,  the  tuner will play the notes allowing you to tune by ear. The
software is Freeware and will work on Windows operating systems.

Systems Requirements:
Windows 95, 100 MB RAM, 30 MB disk space, Java 1.4

Freeware

http://www.guitarpad.com/