PS2 Blues

When the PS2 first came out at $300 I told myself that I would only buy one if I was in the right place at the right time. I wasn't going to be like some of the freaks out there that called every store everyday just to here the same thing, "They will arrive in x days." So one night after work I went to the local 'Wally World', that's Walmart for those who have never heard that expression, and there it was. A couple of PS2 sitting right in front of me. Needless to say I bought it that night and was awed by its power. I've played many games and watched many movies on my PS2 but no more. Some of the games I used to play and movies I used to watch are no longer playable on the PS2, Disc Read Error! I can play/watch them on other people's PS2 but no longer can I on mine. This just perplexes me. I've taken care of my PS2, it cost me $300! I've kept it in proper storage conditions, haven't dropped it, hit it, or anything like that. It just doesn't work! Any ideas/hints/do this/etc would be greatly appreciated.