problems with disc juggler

[Darean]

I think i know whats going on..when i change the .cdi's to .nrg's and burn with nero it does dummy data or something because i look at the disc and it looks like i put like a meg on it or something, it wont load in the comp just freezes till i take out the cd and nothing happens when i have ti in the dc..tho it does say it is a 79min cd..the thing is my utopia cd burned fine with nero but that was already in .nrg format..any clues? or should I only get .nrg games? thanks