I think you've covered pretty much everything I would have tried already, OTR.
I don't have Vista, so I am totally out in the dark with any suggestion I could make here after. My best advice would be to have someone else compile the models for you, Draygoth, once you feel you're done with the texturing/animating in GMax. Not an ideal long-term solution for sure.
I have read about people having issues with programs (games) installed directly under "c\\:program files" (or equivalent). They would refuse to run properly, even with administrator rights, unless installed somewhere else, but I think that was for Windows 7 and I fail to see how that applies to a single executable/batch like nwnmdlcomp. However, if nwnmdlcomp somehow uses or links to NWN resources, and if the game is installed in that directory, well...
Another thing you might want to try is to work at a very low level in your folder structure, with no long directory names, no spaces or complex characters in them. Have everything you need in a folder like "c:\\nwn", or "d:\\work" before attempting the compilation.
Perhaps you could also try to
add that folder to your %PATH% in your environment settings, but unless you weren't the owner/administrator of your computer, I honestly do NOT see why it should suddenly work after doing so.
Lastly, barring a hypothetical debugging of "nwnmdlcomp" (is the source code even still avalaible ?), to see why it fails to link to the supermodel, and recompile a version that would work on your computer, I am afraid I can't think of anything else right now.
Sorry I can't help you better. EDIT : I hope all this won't change your mind on continueing to work on your models however. They look too good to be sacrificed on the altar of some silly stupid Windows Vista quirk.
Sending you my best encouragements ^.^
Modifié par Nissa_Red, 23 mars 2013 - 12:11 .