Cultris needs a decent graphics card to run. Your CPU is almost irrelevant. Further you should not expect that any game is running smoothly on a 7 years old laptop.

My 8 year old HP laptop runs cultris pretty ok, but it heats too much. I had a good run when I had it cleaned up from inside. I used to be faster there than at my current desktop.

What I do is remove all special effects (aero specially) and put a windows XP theme (yes, the old style one).

I used to play on windows and JT gave me this tips :

Open the task manager and shut down every user application.

Shut down explore.exe.

It's pretty effective.

You should also try to unable/disable Vsync. It had various effects on cultris 1.

If you're using a mac, there's also a command that makes cultris use 1 core only. Dunno why but the game is smoother this way.