It seems like the drive went bad. It came with my Dell Inspiron 530, and when I replaced the drive with a new Asus one, it burned fine.
Just to say what my results were.
I am trying to burn the Windows 7 Beta to a DVD+R disc. I keep on getting Power Calibration Errors. I have tried three discs, all from the same store bought stack, all of which fail. Tried lowering the speed to 6x, but the same problem happens.