Music CDs use to play and now don’t

A friend of mine has a Gateway PC that he has been playing music CDs on that were burned from another computer. The CDs were working fine and now they won’t play at all. He can play some CDs and some he can’t. He is running Windows 98 and as far as I know hasn’t done anything to his computer as far as adding new software or hardware. I do believe that he had to reinstall Windows over itself previously due to a modem problem but I don’t know if that is when the problem occurred or not. Any suggestions are appreciated. Thanks.