Dirt ,smuges or anythink stuck to the CD can cause it to skip. Scratches can also cause it. Sometimes the CD only has to be cleaned to work properly again.
The CD might be fine, skipping could be caused by the CD player too. Make sure the lense (where the laser comes from) is smudge-free and clean. There are disks you can buy that will gently clean the lens. Note this may not be necessary, check if the CD is at fault first.
