SONY DVD-ROM DDU-1621 S1.6 16X,40X

HI THERE. I AM A NOVICE PC USER AND I WOULD LIKE TO ASK YOU HOW CAN MY DVD-ROM READS CD’S AT 40X AND DVD’S AT 1X?IS THIS A MECHANICAL(TRAY PROBLEM,LAZER..)OR WHAT?I RUN WIN XP PRO SP2,MY ASPI IS WORKING OK(SYSTEM AND NERO 6)AND THE DRIVE IS SLAVE TO SECONDARY CHANNEL.ALSO UDMA MODE IS TURNED ON AND I USE THE LATEST DRIVERS FOR MY IDE CONTROLLER.