Philippe, you'll need a device which takes the digital output from the USB port on your laptop and converts it to a form which an input on your 5003 can accept and process. One reasonably priced item is available
here which works by converting the USB output to optical digital data which you then use an optical cable to feed into the optical input on your 5003.
The quality of the sound sources available through your computer varies, and doesn't match the excellence of the CD format, but can be quite acceptable. I listen to a great deal of classical music from stations when I'm on my computer (KUSC at the moment), and the great variety available makes it enjoyable, even when the sound quality isn't the ultimate.
