DailyTech writes Microsoft has released a fix for the Windows XP SP2 battery drain problem that occurred on the Core Duo platform:
The problem apparently plagues Windows XP notebooks that cannot correctly enter into processor idle sleep states, or C-states. When the processor cannot enter these states, the processor idles, but at a higher state. The result is wasted battery life and a slightly warmer CPU.
There are many reasons why Windows XP SP2 does not let the CPU enter into the correct state, but the one reason seemed to revolve around notebooks that have USB controllers that do not turn off..