Microsoft has posted a fix for a driver flaw that prevented owners of Windows XP Service Pack 2-based notebooks from taking advantage of power-saving sleep states.
The flaw occured when notebook users plugged a peripheral USB 2.0 device into their notebooks and noticed a precipitous drop in their battery life. Mobile processors use a variety of sleep states that put the processor in an idle mode when its workload lightens, conserving power consumption and extending battery life. But the flaw prevented those systems from entering into the deeper sleep states when using a USB 2.0 device.
The download is available here.