The first batch of PS2's(the ones produced the 6 months after it was released) had faulty optical lasers, which weren't powerful enough to read certain discs, so Sony had to recall them to fix that problem. Old and new PS2s also have slightly different hardware. If you actually open them up, you'll notice the changes. If your friend still experiences problems, then have him call the company and ask for a repair. They'll do it for free.