wii optical discs (original dvds) can be read only using a particular drive on PC (LG something) wich is compatible with rawwerite (the only software that can dump wii games)
the problem is not due to the image format or files in it, it's encrypted, we all know that, but it's a matter of "disk physical layout" wich is different from a normal DVD.
infact, in a wii disc (differently from a DVD-ROM) sectors are placed so that a constant rotation speed is required for the disc to be read.
in normal DVDs the internal part is read at faster speed then the external one, becouse sectors are placed at the same distance from each other all across the entire dvd.
in the wii disc instead sectors are placed on a different distance (have different lenght) so that a constant speed is used to read both the internal part and the external one.
this concept is only valid for ORIGINAL wii discs, once an ISO has been dumped, and burned onto a DVD-R, this copy can be read with any dvd-rom drive for PC.
that's becouse the dvd burner can only write sectors in the standard dvd-rom format (equal sector distance)
this is also the reason why using dvd-r intensively on a wii optical drive can damage it, becouse it reads the dvd-rom in a format wich is not the one he's expecting, and even if it works (couse the standard is supported by the firmware) the mechanical parts are affected.