i did some research and found out 2 things:
1: the models for the years 2000-02 had problems with the dvd player wearing out, which resulted in a complete wearout of the drive itself, making it impossible to listen to cds, play games or watch movies
2: 2003-2004(not including the skinny ps2), sony made a delibrate decision to fix this problem by using CHEAPER dvd playing hardware. the theory was that if u burnt them out, u can send them in for free since theyre so cheap. doing so=happy customers. happy customers=profit. right? wrong.
the thing is the new dvd player hardware is SO cheap that it cant read certain formats of dvds, certain encodings, certain copy encryptions and SOMETIMES just plain didnt work. but u could still play games.
the thing about the skinny ps2 is the same for the original ps2's from 2000-02, u can wear it out. BUT sony did fix the skinny one by micosizing everything, effectively making it "cost-effective" to have it burn out. dont ask me why they put it that way, they just did. i dont get it myself....