Just to maybe help out a bit more, what you need to connect the keys to the computer is one of these.
Option #1.
http://www.m-audio.ca/products/en_ca/MIDISPORT1x1.html
I think you can get them for around $50. If your sony recording software supports midi thats all you need.
If not you need a copy of something like Cubase LE which supports midi recording.
Option #2.
As some mentioned before to record Audio to the PC you should really invest in a recording interface.
http://www.presonus.com/products/detail.aspx?productid=43
Something like this should handle all your needs, it includes a midi controller so you don't need the m-audio box I mentioned above. I think these run for about $500. This comes with a presonus DAW program. This would allow you to Record midi, edit the midi on the computer and then send it back to the keys. You could then record the audio from the keys back into the computer.
Hope that all makes sense.