As please stated, you don't need to have two drives to copy a disc.
One way to accomplish it with just one drive is to burn to an image file, then burn that image to a CD-R. In Nero Express' Preferences/Expert Features check the Enable all supported recorder formats for the Image Recorder checkbox. Then you can select Image Recorder from the What drive would you like to use? drop-down box.
You can keep the image file on your hard drive in case you need to burn another copy in the future without having to read the original disc again.