You would also have to remove the MPC500 from the PC and USB mode.
Then load the files into the MPC500 from the CF card.
Another way would be to install a dedicated CF reader onto your computer, then you wouldn't have to switch the MPC500 over to USB mode while connected by USB to your computer. You would just take the CF card out of the MPC500, put it in your computer's CF card reader, save the files onto the CF card either directly from Cool Edit or within Windows Explorer, then put the CF card back into the MPC500, and load the files into the MPC500.