For a freeware application that'll handle the recording and any subsequent editting you may want to do, you can't beat Audacity, which you can find at
http://audacity.sourceforge.net/ - some instructions for it's use are here -
http://www.transom.org/tools/editing....audacity.html.
You'll need to attach your cassette player to your computer, through the Line-In jack, which is the same type of jack as the one on your headphones. You should be able to get what you need from any Radio Shack (or other electronics store). Tell them what you're trying to do - they'll know what you need.