There's pretty much zero chance of *any* version of dolphin running on that pc - a dx7 era GPU simply won't work, even if you used the *extremely* slow interpreter cpu backend (removing the requirement for 64-bit - but it will literally be impossible to play enough of the game to actually dump a decent sampling of textures before you're old and grey...)
The amd athlon x2 would be quite a bit faster than a p4 - you say it doesn't use windows - what OS does it use? Dolphin supports more than windows remember.
And as for poking around in the game iso image directly - the formats used aren't standard over all gamecube/wii titles, it's up to the game devs to decide what to use, and what's supported by their engine. It may be others have already decoded the formats used in each specific game, or they use a relatively well known standard format, but that's kinda outside the context of the emulator itself.
The amd athlon x2 would be quite a bit faster than a p4 - you say it doesn't use windows - what OS does it use? Dolphin supports more than windows remember.
And as for poking around in the game iso image directly - the formats used aren't standard over all gamecube/wii titles, it's up to the game devs to decide what to use, and what's supported by their engine. It may be others have already decoded the formats used in each specific game, or they use a relatively well known standard format, but that's kinda outside the context of the emulator itself.