Hi Man

For some reason Maya dosent seem to like hyperthreading, also make sure that you enable multi threads or maya willl just use one core.

Theres a thread on the subject over at cgtalk about "fastest render in with maya 7/8" (thats not the thread title but you'll see it if you have a look in the maya thread) The guys there show the settings etc so you can post your settings and get some advice.

Hope this helps you out.

Cheers