If you want to record your performances to your computer AS THEY SOUND from the keyboard, you are going to have to consider investing in a USB Audio Interface or a software generator where the sounds are actually stored on the computer.
Most guys are coping with videoing their performances and posting links which is fine and is cheaper to do. I should say, the other method mentioned above would provide a better sound quality and will give you more control over editting and arranging performances using more than one layer or sound at a time.
I currently only have a MIDI Interface which needs something like Pianoteq to play a "voice".
I was trying to download the demo version but there seems to be a problem with the download.
Your's seems fine but I know the one in my laptop won't!
Good point though - I had forgotten about that because it didn't suit my computer at the time.
Most guys are coping with videoing their performances and posting links which is fine and is cheaper to do.
Make use of the Gbuttons. Theyre extremely useful.
Edit: you also have the same external HD I have.