Windows already has 'Sound Recorder' included for precisely this purpose. Very basic, but it works. Email me if you need help in setting it up (PM doesn't support attachments!!).

Sound files soon fill up your hard drive, so get a CD rewriter if you haven't already got one - they are so cheap these days.

Alternatively, you can change the quality of the recording - 8 bit mono at 11,025Hz sample rate gives relatively small files, just about acceptable quality for speech; 8 bit mono at 22,025Hz is the lowest acceptable for music.

Full CD quality is 16 bit stereo, at 44,100Hz, but files are typically around 50Mb for an average length song. My first hard drive was only half that!

You can always use an MP3 converter to squish your big .WAV files to a tenth of their original size, but it starts to get messy!

Cool Edit and Sound Forge are 'heavyweight' programs which do the job well, and allow you quite complex editing possibilities, including multi-tracking. They allow you to save directly into MP3 format, too.