Kinda funny that it only works on fake multi-core CPUs, and not real ones. :P
Yeah. This kind of thing is why i can't stand the CPU/GPU wars. This was probably some crazy deal with Intel.
Well, Igor8472 has a C2D, so apparently it specifically needs to be a Intel HT for this to work. Mine is a PIV 3.4 HT and i can confirm advanced particles are ON.
From the game FAQ at Codemasters:
"Problem: It is not possible to enable Advanced Particle effects in the game."
"Solution: This option is only available if you are using an Intel Pentium Processor with Hyper-Threading enabled."