connect your FM transistor radio(the one you get i market for 50 bucks) to the line in port of your sound card, use a stereo cable with 3.5 mm jack at both end (25 bucks) put one end of it to your radio to earphone socket another to line in of you pc sound card, you are done.
PS:- u have to change the channels from the radio itself.
this is the cheapest and ready to use solution