Try copying the DVD files from the disc into a temporary folder on the desktop and see if any errors come up when you do this. Don't try and play the files from the hard drive though as most DVD's are copy protected and it won't play properly. But if you don't get any errors when copying the files then it's a software or codec problem as the disc can be read fine. Try playing it in something other than PowerDVD, my first choice would be Windows Media Player as PowerDVD installs the MPEG-2 codecs that Media Player needs anyway. Then try a few others that you can get hold of. Obviously if you get errors when trying to copy the files, then the disc is damaged. Optical discs don't wear out because of how they are made so it will be dirt or scratches that cause the read errors - if it was one of his favourites then it could have been out of the case a lot and be subject to damage.