Clean lens for xbox 360
How do I clean Dirty laser lens
well you have two options. You can try one of those cd's with little brushes on them or you can follow this guide then remove the four screws holding the drive together and from here you can remove the top case and take a cotton swab with a little bit of rubbing alcohol on the tip and gently wipe the lens off.
Hope this helped,
P.S. The second way will void any warranty you may still have on your xbox.