Sure there's a way to do this... if your computer has a sound card, then you have this capability already.
A few steps to achieve this:
0. Connect your phone line to your line in input (not as trivial as it sounds)
1. Digitize the data using your sound card (this will turn it into PCM audio)
2. Save your PCM data to WAV file (uncompressed audio)
The tricky part will be connecting your analog telephone line to your line in input. Reason being that you have to make sure you don't burn the input with levels that may be too high (consult your sound card manufacturer for appropriate levels).
After you've figured out the voltage levels, you can simply control your capture using the Windows API's for sound capture. Something like
this[
^]...