At this point I can semi-safely say that I got a bit too carried away with the mipmap stuff -- after trying edits to the common-objects-file, it's becoming more apparent that it isn't as relatively easy as I initially described. Disregarding the fact that G-TXD adds transparencies at seemingly random to a few files that neither need nor should have transparency (and it does so without an alpha-channel, to boot ), adding mipmaps to custom texture packs generally seems to make the game crash anyway. Why it didn't crash with the common effects textures is beyond me, though. EDIT: Hm, upon closer inspection, there's three major differences between the Common effects and common objects archives : The effects one is full of textures with alphas. According to ViceTXD, in the effects one's header, Flags 2 and 8 are on for every texture -- whereas in the objects one, it only lists flag 2 (and flag 1 for files with alphas). And third, for the Alpha check (true/false), it lists them all else false in the Effects archive, despite there being Alphas present -- additionally, a very long number is listed after it as opposed to a 0 or a 1. (the number is randomly 861615636 or 827611204 on the files -- I cannot decipher a pattern to the placement of those numbers) I have no explanation for that last change but somehow, it makes the game read the file perfectly fine. Gonna try to recreate my steps more accurately, I suppose… 'NOTHER EDIT: FINALLY figured out where I went wrong. All this time I was assuming Vice City's was the format to go with, since just about every software I used identified the game's files as being Vice City Format. Saving the TXD with mipmaps in G-TXD in San Andreas format, however, that did the trick and apparently, that's what I musta been doin' with the effects textures as well. Finally this whole thing is making sense. Sorta. The only problem that remains is that G-TXD (at least for me) imports some files with transparency without giving me an alpha-channel to work with -- as if there was a bunch of colors that are inherently transparent. That causes stuff to be transluscent of course, and when not intended, that looks shitty in games -- case in point. I have the theory that saving this in Vice City Format first without mipmaps allows for such faulty textures to be replaced with their real counterparts in Vice TXD -- then, it should still be possible to create Mipmaps and make the whole thing an SA file usable by Heroes. Gonna test that tomorrow, 'tis 5 am and I wanna sleep.