WINSCOPE is a software application that will use your sound card to sample input waveforms and display results.
The Oscilloscope allows you to study any signal in real time, measure frequencies, study realtime signal spectra and plot Lissajous patterns. In addition, winscope also has a storage facility and has a powerful FFT (fast fourier transform) routine, which enables winscope to act as a spectrum analyzer.
AUDACITY is free, open source, cross-platform software for recording and editing sounds.