If it is a backup game just use Nero to do a disc copy. You can also use IMGBurn by doing a READ then WRITE. If it is an original game then you will need a BBA (Broad Band Adapter) to network your GameCube and computer. You then need an operating system on your Modded GC like GCoS that has capability's of backing up the Wii game. You can not stick an original GC game into your Computer DVD drive and make a copy of it.
So for burning though, DVD Decrypter is fine? Not for making backups just burning, cause in order to make a backup you need BBA and other stuff?
I would just drop the whole BBA, Crossover cable and Reciving app proccess thats a headache and outdated the most simplified way to do it is by going to NewEgg.com ordering the LG-8164b DVD rom for 17.99 and downloading Rawdum 2 just stick the GC games in the LG drive run Raw dump 1 1/2 hours later Wa-La! burn the ISO pop it in , oh yeah make sure you got a modchip installed unless your using the PSO method
