one thing...Wrong forum.......try Main forum, dont be surprised if it is moved.....
try cleaning the lens with a lens cleaner (it is a CD with brushes on it) or turning it verticle. If that doesnt help and it is out of warranty either A) Call sony or
Open it up and use canned air to clean out the inside of dust and if you are really adventureous increase the power to the laser, Gamefaqs has a Faq on cleaning the PS2.