Jim, others have addressed your question assuming that you already have the computer interface. Is this true? That interface requires an integrated circuit chip plus an interface in a cable. Kenwood previously sold both the chip and the interface. They are no longer available from Kenwood. However, there is an alternate at http://hosenose.com/interfaces.asp
. You need both the LCU-3 interface (replaces the Kenwood IF-32C) [at $45] and the chipset [at $14]. I'm not sure what the shipping cost would be to you. I used this duo when I had my 440 and worked many stations on different digital modes using MixW.
Of course, you also need the sound card interface (discussed in the other messages) to enable you to encode/decode the digital modes. I personally use the RASCAL one, and it does great.