Finally got it!!! I think it had something to do with the skins being zipped, since I downloaded them all from within UnleashX. I unzipped my favorite skin and put the intromovie.wmv file in the same path. It's one of the many combinations I tried before, except no zipped up!
I also, updated to 0.38, but I don't think that had anything to do with it as I tried changing settings after the update, too.
Anyway, thanks for you help, Jezz_X!
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On a slighlty similiar note, how would I go about removing the "flubber" Xbox boot screen? I know it can be done with BIOS settings, but will that remove it permanently? Will it just remove when the mod chip is enabled or always?