Hi. You could try cleaning the lens. Take top off, you will see the optical pickup. Here is a picture of one
http://zekfrivolous.com/faq/sam/k38n.gif
Get a cotton bud, and wipe the lens (don't need any fluid, just do it dry).
If it still won't play, then the pickup has probably died, and it's into the bin she goes. The pickup should last 3 to 6 years and thats your lot. They de-grade even if not used.
Mark
May 2008