Today Microsoft released a patch that corrected a bug in Windows that caused Mobile CPUs to drain battery power more than they should. This is a well documented problem. http://support.microsoft.com/kb/918005 I installed the patch on my MBP under XP. Low and behold the battery life increased by about 30 mins. Awesome......... or was it.... The Whine was now in XP as well!!!! Previously there was no Whine under XP on a MBP and people had correctly assumed it had to do with the power management driver. The MS KB article says: ...... prevents the processor from entering the deeper ACPI processor idle sleep states, or C-states. C-states save power when the processor is not busy. These states range from C0 to C3 or C4. Typically, an idle portable computer uses the C3 and C4 states to preserve battery power. If an idle portable computer cannot enter or maintain the C3 or C4 states, the battery power drains more quickly. This problem is fixed by installing the download that is available in this article. Intriguing isn't it. The good thing is that the patch can be uninstalled if one wishes.