What brand of processor is it, Intel Core2 series or an AMD processor?
On normal desktop computers AMD is quite a bit weaker than Intel's Core2/Quad/i7 line of processors. Anything based on the Phenom architecture should run some games full speed depending on how demanding they are, while running most other games at half speed or slightly better.
Even beastly machines with overclocked i7 processors still experience slowdowns in some games.
If your processor is based off of an AMD Athlon64 I would not expect to see better speeds than that for this game and other games, some games might run half speed at most.
You also need to enable the TLB hack for this game, make sure Dual Core and JIT Dynarec is enabled as well. You should also use the OpenGL plugin since your graphics hardware supports it, don't enable AA or Vsync as those options cause slowdowns, lag, and stuttering in the latest revision.