If you continue clicking through the messages you should eventually get to your files. What the messages are telling you is that there are files missing from your iso. The thing is that this normally wouldn't be much of an issue, but for modding it is such a pain because you have to click through all of these messages each time you replace a file. I know this because when I was starting out I went like a month clicking through those. You should get a new iso, preferably an ntsc one instead of pal, in order to save lots of time.
Just for reference, a good ntsc iso will be like 7.9GB in size. I think pal is like 7.8GB.
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edits: The other time you'll get these kinds of messages is if you try to edit the iso while dolphin is still reading it.
The reason I think you should go with an NTSC iso is more files and codes are compatible with it. Though, if you have a
non-USA Wii and might eventually want to mod your wii to be able to read your isos you may want PAL. Of course, with the nintendo network shutting down soon there won't be much of a purpose to playing with it on a wii anymore, unless your computer doesn't handle it well. But if you live in USA just get ntsc.
