Also if cleaning the recorded side of a CD always use a lintless cloth and only make straight wipes from the center hub to the edge (think "wiping spokes on a bicycle tire".) CDs are expected to have some spurious bit errors and there is a good error correction algorithm to handle that. The data are written as one continuous spiral and if you wipe it in a circular motion it increases the odds that multiple bits in a row could become damaged rendering the ECC useless.