I have a 3.0 Ghz AMD Phenom II X4 processor, and 4GBs of RAM. The game lags a bunch when things happen. Any bombs going off, or >10 AIs going on seem to drop the FPS significantly, any more, and it can become unplayable.

It depends on your perspective. That could be your Automatic Awesomeness-triggered slomotion

Seriously though, CC shouldn't lag that bad. What Fps are you getting normally? how about with two incendiary grenades at the same time? that seems to be a good performance indicator.

More importantly: what resolution are you playing at?

It shouldn't be too bad. As said before, try moving to a lower resolution.
If that doesn't work, try this thread.

It doesn't really require much of any extra coding. Using pricey compilers, such as the Intel C/C++ compiler with OpenMP support, would enable them to easily take advantage of multiple cores with a simple directive before their logic loops. So your answer is correct but your reason is wrong.

IE: This would take 100% time on a single core machine, which I am sure no longer exist, or 25% of the time for a quad core, or even 12.5% with a new Sandy Bridge i7. And note that the single #pragma is all that is required to make that multi-threaded.

Actually, there are plenty of single-core machines, I only recently switched to multi-core.

I play on a i5 stock with 4GB ram at 1024x768 and it works perfect

Ew, large resolution cortex command.
That said, it's good to know that newer processors are happy with it, it's just such a shame that older machines can't play a game marketed as "retro stylin'" or whatever.