Just out of curiosity, why would you want to disable that timer??
From what I have read this HPET (High Precision Event Timer) is the successor of the RTC (Real Time Clock) and is essential to keep your computer running.
Disabling it, even if it is possible, can cause all kinds of problems as every circuit in your computer depends on it.
HPET not only controls the clock rate your processor runs on, it also provides high precision interrupts and provides all the clocks for the peripheral equipment (Video card, USB controller, sound card etc.) and your display as well.