Toribash
UPDATE

Even with shaders disabled the game sometimes lags with a system like mine with no interfering background apps.

Deinitely something a little off. My suspicions lie still in Vista 64. Running in compat mode for XP was no use.
PLEASE NOTE! Toribash only makes use of one core.

I have two processors, both 1.7Ghz and dual core.
Runs great in windows, but since toribash only uses one core of one processor i only get 1/4 fps of what I should get.

Always expect toribash to lag sometimes mate, its very hard on the processor.