Emac Dvd Problem


I bought an Emac 2 years ago and let it sit past it's warranty. Basically since I got it it won't play a single dvd through to the end, I always get this error message:
DVD Player encountered a serious error.
There was an error reading from the disc. It might be scratched or dirty.[-36]
This has happened with brand new dvds.
The particulars:
Memory: 640MB
Processor: 700 MHz PowerPC G4
OS X.2*
*After purchase my friend installed OS 9 as well to allow for certain music software to run. He also partitioned the machine into three drives, OS X, 9, and DATA. OS X has 6.6 GB free. That's where I play dvds from, or try to at least.
The drive is a CDRW and DVDR, I haven't had any real problems with the cd part of it, but it is senstive to skips.
The dvd player is version 3.2
Disk Utility repaired some permissions but didn't solve the problem. On another attempt it crashed.
I've been all over the web looking for a solution. Apple won't answer my emails. I'd appreciate any ideas. I'm not too saavy with Macs so please be detailed.
Much thanks!
O.K. Just one question, if this has happened since you bought the Mac, why didn't you contact Apple right away?

So if this has been an on going problem, then you have limited choices. First you should zap the pram. If that does not help, try a Safe Boot. If that doesn't help, replace the drive.
Why did I not contact Apple right away?
Everyone I spoke to basically thought it was a simple problem with a simple solution. In short, that the problem was me and not the shiny new computer. And as I barely used it for a year the problem took awhile to seem significant to me.
Thank you for your suggestions. They didn't work though, the safe boot won't let you use the dvd player anyway.
http://www.videolan.org - get that software and see if it can play a DVD to the end or it ends up the same or in a similar manner... It's not as nice an application as Apple's DVD Player, but it basically does the job. And it'd certainly be interesting to see whether the problem is really hardware based...

Btw.: Can you boot that eMac from OS 9? And does its DVD Player act correctly or not?
The OS 9 dvd player does the same thing, the error message is different but it crashes midway or so.
I once tried to install another dvd player and the computer wouldn't accept it. I'll try it again.