Grinding or slipping DVD+/-RW drive on Dimension E520

Hi, I have just bought a new Dell Dimension E520 pc. The pc is great but i have noticed when putting a cd in the drive, once it picks up speed it grinds rather loudly and sounds as if it has thrown the disc off. Sometimes it corrects itself and other times i have to eject on fear of damage to the drive. But when i play a DVD or burn a DVD i dont have that problem as it runs at a slower speed. I havent contacted Dell yet and i really dont want to post the whole pc back. Would rather post the faulty drive if its faulty. Any suggestions?

 

Thankyou,

 

William