Why won't my DC play nero burnt games?????

[total package]

For both of you guys.
If you downloaded the file in the internet, most likely you downloaded a *.cdi image which is created by DiscJuggler and ONLY can be burnt through DiscJuggler.

If you want to burn those games through Nero, download (I forgot the name) an application that will convert those *.cdi images to *.nrg.
Now, those *.nrg files can be read by Nero and burn it.

I hope this helps a little bit or gives some an idea.