None that I'm aware of. I've never consciously downloaded an A/V codec on this PC. ffdshow apparently came bundled when I installed SmoothVideo last year, so that's gone now. I don't see anything else suspicious in my programs list.

My efforts are paused for now, anyway. I respect this game and I don't want to mentally associate it with being annoyed for hours on end D: Better to save it for a clean test environment. That'll probably be in the next 3 months, because now I'm starting to notice other games in my library having similar freezes, eg. Darwinia.