djmykey is right. The procedure to do this has been discussed many times in this forum. A simple search for "cassette" yielded the following results:
*www.thinkdigit.com/forum/viewtopic.php?t=18272
*www.thinkdigit.com/forum/viewtopic.php?t=5615
*www.thinkdigit.com/forum/viewtopic.php?t=294
*www.thinkdigit.com/forum/viewtopic.php?t=10066
There are probably more guides out there...