Subterranean

Quick question about a basic project I thought of. I do have a small amount of knowledge of electronics as I have done a physics degree, however it is obviously lacking. I own an mp3 player that will recharge its battery either via AC, or USB when plugged into a computer. The AC adapter that comes with it is rated at 5V 2000mA (2A). However the USB standard is rated at 5V 500mA, i.e. a quarter of the current of the AC adaptor, and as you can imagine, takes ***ages*** to charge through USB. My question is; would it be possible to link 2 USB cables together, so that when both were plugged into a computer or powered hub, it would output 5V at 1000mA by combining the current, and keeping the voltage the same. Obviously I could just splice the +5V wires together, and the GND wires together from both the cables, but wouldn’t this just give me 10V at 500mA? Correct me if I’m wrong, as I said I don’t have that much knowledge in the field. Is there any way of doing it without having to have a ‘box’ of electronics on the wire? Obviously before plugging anything into the player I would check with a multimeter what exactly was coming out of the thing. Thanks for any help.