Why do external cdrw drives cost so much more than similar internal drives? A friend of mine has a case that has only one drive bay(which has a cdr drive) and would like to add a cdrw. I guess the best way is to add an external usb one, right? Or maybe I could swap his parts into a new case and buy an internal cdrw. It's an HP machine and I am not sure all the HP stuff will mate up with a new case. What would you do in this case?