Why do the original (thick) Playstation 2 tend to stop reading the PS2 (reflective back) disks after awhile?
This is a common problem with the PS2, especially the original ones. The problem is that the laser has become misaligned with the lens. You might be able to try cleaning the laser lens and get it to work temporarily but in the end that will only make it worse, as strange as that may seem. There is no free fix. Sony could fix it for a fee but you’d have to pay for shipping to and possibly back to you. I don’t want to tell you the bad news but there is no way you can fix this. The cost to repair it would not doubt be expensive and you’re better off saving the money to get a new one (or save up for the PS3).