u need a cable with Stereo jack on both sides....
do this:-
1]connect ur FM radio to Line In (or Microphone) of ur PC.
2]Next, right click the Volue Control icon in System Tray, and click "Open Volume Controls".Here go to Options>Properties menu.
3]Select the Recording radio button, and in list shown below Select (put check mark) the Line In and Microphone and click OK.
4]In the main window, u make sure that Line In is selected (not muted),and keep the Line In Volume slider to max.
5]Get a software called Audacity, and install it. After this go to File>Preferences in Audacity.
6]In the Audio I/O tab select the Channels as "2(Stereo)".
7]After this, connect ur FMradio to Line In of PC and click Record button in Audacity.
*audacity.sourceforge.net/