Editing files on copyed discs, possible?

[Miles McCloud]

I have no interest in pirating games, or even burning back-ups (All my games work). But I am interested in editing the files on copyed DC discs. After much work I managed to find and download Jet Grind Radio (I own the real game). I then burned it. It worked fine, selfboot and all. I then copyed from that disc to my PC. I used "Dreamcast Movie Creator" to change the ADX sondtrack. I altered some of the HTML files on the disc, editing the existing JPG files to some graffeti tags I made, so I wouldn't have to go online to use them. And finally I changed some .gif files which appeared to be the charactor icons. The files all added up to about 600 megs . I then burned these files to a new disc using Nero. I hadn't tryed for selfboot, because I don't mind using a bootdisc.

I then tryed booting it using the Utopia bootdisc. The disc in the background changed to the JGR disc, It showed the little loading percentage, and then it took it to a blank screen. Thats all I get.

I've tryed burning several times, and have made about six coasters. I've searched around the net, and found some info about about hacking boot files and using dummy files. However the instructions were in a differant language and Google doesn't translate it well XD.

Is there some step I'm leaving out?
Or is it simply impossible to make the changes I made? It would be uber-cool to play JGR radio with a new soundtrack. Many many thanks in advance.