I tried all combinations, actually. Software Mirroring, Transparency, and that other one that eludes me, right now. I tried installing the fixes featured here on GoG, but they're incompatible with my saves. I don't think I have the strength of will to test what will work, considering the length and difficulty of that battle...
Guess I'll just visit a friend who has an older machine and WinXP, complete the fight, then continue playing on my own PC. A backwards solution is still a solution. Still, some sort of warning or recommendation on the item's store page regarding optional fixes and potentially severe problems with newer machines would have been nice. The reason I bought this gem on here is it's supposed compatibility with new machines.
Well, that's enough of me hijacking this thread.