Check your CPU utilization and you may also need to set processor affinities. Note that it likely may be your GPU. I would crank down all the settings (uncheck everything in effects, and set every slider to the lowest. Turn down your resolutions to 800x600 also and see if that helps. Also set your maxfps on your clones to a low number.

Note that I 5 box on:
- A thinkpad t60p laptop with dual displays (Duo core cpu)
- It has a CAD workstation class GPU (FireGL 5250 256mb)

So it is possible but turn down your graphics settings. I consistently get 30+ FPS even in Dal and Raids. But my CPU can't handle dalaran well (it is pegged) but elsewhere and in raids it runs at between 60-80%

Good Luck.