Create an own Iso/Disc

[Manaplayer]

Hi!
My question is, how to create a new Disc (Don't have to run on real system, only on Dolphin).
I want to mix files from to disc to create a "new" game of it.
I know that it's possible to extract files of a disc, but not how to create all extracted files to a new disc / iso.
I don't want to burn a real disc - Only a iso file for Dolphin.
Thx in advance