Every gameplay vid I've seen shows clunk, clunk, clunk, so I don't think there's any fixes, short of someone taking up the cause to fan-patch/source-port the game. The 25th Anniversary is coming up, so it's certainly possible that Rebellion could revisit the code and poop out an update for modern systems, but there's no sign of that happening.

The game is old yes but its fun and mostly good adventure horror. But yeah if only someone could patch it up for 60fps that's the only fix it needs ever. Also Rebellion rebooting or re-releasing this franchise is highly unlikely as I'm sure they don't have rights to "The mummy" and its universal studios that has it and eventually the game wasn't reviewed well (cause game journos suck then, today & forever) and don't know if it sold well. But there are more middling games than this that have been made to work better on modern PC. So why not this? It's the only good 3D"Mummy" game that exists after all. 60fps and modding support like able to change textures and editing character models would bring this game back to life.