Problems Installing Tiger on my Powerbook

I just purchased a used 15' Powerbook G4 1.33ghz with 1.5gb of ram. It's running Panther very nicely, but I'd like to upgrade to Tiger. I bought a burned Tiger install DVD from a guy on Craigslist, but I'm having touble installing the OS. Everytime the download reaches about 60% it stops and tells me theres a problem with the disk of some sort. I took the disk back to the guy and got another one, but the same thing happened. Is this normal for this machine? (this is my first mac) Or should I being doing something else? Do you think his desk are the problem? Thanks in advance for any feedback.